. . . . .- , «1“«ww.“v—.-‘_W___4“4_. ., , 4, . , . .. 2 4 . . _;. , ’ .x.‘ 7 , 1 . . ’ ’ - ~ ' ' w " SELECTIVITY‘ OFCYANAZINE fa; . '2 ‘ » . » ' (2444‘ c-Hmm;5 (HHYLIIMIHII, * . 1' w s TRIAzIN+2 YLIAMINO] 2- ~ METHYLPROPIONITRILE) 0H FALL * ~ - PAHIcuIH IPAHIcIIIH DICHowMIPwHw -j «* . ,- MICHX)GREENFOXTAIL . . (SETARIAVIRIDISL)AND - * ‘ " CORN (ZEAMAYSL) .- ,. /.... /‘""r-.”a:ua , . I ' ( ”I ,, {v.1}. I 4 ‘c. I 4. ”’ 1., , ”a ”11‘ 4f 1Mft’.r"4di" (“4, 141 , . »1.(l’ . Jul, p Y 1 ... . .4”; f4";- , ~_v-;~r~ 44,. .r p ,. ,,- 4 0-? {—1.411 ~44» 1_ - , 14.”, , ,4, 44 r » :1. ”Egg. ' . ‘ :.'.,'.'?::;m-,- , v ’;::,7,‘ v 4 ‘ g. . fangs; " " - - 1 - ‘47"; v Pint-fr 1.41.. .4 , v _ - . ’ ”I «p I! 1" ' ’ ' L1.” (41m; ' M pg... 1 r .4 new m'r-sz-s in ' . .4‘.',".‘1..’.,4v.4 I. ' ‘ 1», - ,4.1_.0-i. ,I.,,.4.4.4~;-u- -- 1 . ”1", , £wa -4--- _.,”;;', “My; 1 4 4, .3 - . :h’a’.‘ :&v. r ’1 - I' J; ' J ’ " * ” 5* -‘:¢:rW 343’» v: —r,i?"Va"-'r~w ‘ ”if, wuw “1-91-th - ‘“' m? fin"? r4"? , I ,p , .32.; 1")0‘01’):IG fiff’JM . FA,“ 1143'», 1-, p t« w! -;u¥r-d 121552, 3’51”"! 4f0éyyr ff '29M44'2fi42mw ,,“.,.'..4...,. I ,,.I ,4 , ,......l _ . 4’41rr02lll‘J-rlfi a. . 1, , ,_ - yrr'nvw wlrt: . .,.. I’ 4’.’.,"."..,. '..."” Iii-A'e‘frn‘ ‘ v-u ::""“?” III/$73111 v Ii r~fr/.-a.;r"',{'7""' lit: 'fi§¥'€flr*“"" ’3'” ,,,,;;, 4y”. I 213” {trait-pf 1740311341», . L . , I ,t ' “,1 V ‘11.»?! 4. ‘,f,’,"',,...' . .4 4... 4 4- 4-1/1!» 4 , 2 , w .H, .4)” ; J 4 .. .,. ., “4. ' ., U- 24 u ‘u .4” r. LI B RAR Y Michigan State Univeu'uy This is to certify that the thesis entitled SELECTIVITY 0F CYANAZINE (2—[[4—CHLORO-6-(ETHYLAMINO)— g—TRIAZIN-z—YL] AMINO]-2-METHYLPROPIONITRILE) 0N FALL PANICUM (PANICUM DICHOTOMIFLORUM MICHX.) , GREEN FOXTAIL (SETARIA VIRIDIW (& MAYS L.) presented by Albert Dean Kern has been accepted towards fulfillment of the requirements for PhD degree in Crop and Soil Sciences LOW: WNW I Major professor I Q 0 Date (J‘aqm 30f “’7’" 0-7639 ABSTRACT SELECTIVITY OF CYANAZINE (2-[f4-CHLORO-6—(ETHYLAMINog-§fTRIAZIN-2—YL] AMINO]-2-METHYLPROPIONITRILE ON FALL PANICUM (PANICUM DICHOTOMIFLORUM MICHX.), GREEN FOXTAIL (sETKfiiA VIRIDIS L.), AND CORN (§§§_MAYS L.) By Albert Dean Kern The response of corn (Zea mays L.) and fall panicum (Panicum dichotomiflorum Michx.) to postemergence herbicide applications at three stages of growth was examined. Early postemergence application of cyanazine (2-[[4-chloro-6- (ethylamino)-§ftriazin-2-yl]amino]-2-methylpropionitrile) at 3.4 kg/ha provided the best control with minimum crOp injury and greatest corn yield. Hand removal of fall pani- cum at the 7 to 8—leaf stage resulted in corn yield reduc— tions of 25% as compared to plots which were weed—free from the 2-leaf stage. The addition of various adjuvants in— creased cyanazine activity on both fall panicum and corn in field and greenhouse experiments; however, field trials showed no differences in grain yield at harvest. In the greenhouse, less corn injury was observed with a vegetable oil additive than with other adjuvants. 4 Albert Dean Kern Greenhouse studies indicated that root absorption after postemergence application of cyanazine enhanced phytotoxicity to fall panicum, green foxtail (Setaria viridis, L.), and corn. Less 14 C—cyanazine was taken up 'by the foliage of corn than by the weed species. A lower concentration of parent cyanazine in corn leaves was also evident. The addition of a phytobland oil to the treatment solution resulted in increased foliar cyanazine absorption 1 and 5 days following treatment. Although rapid metabolism occurred in corn roots, the large amounts of cyanazine ab- sorbed via the root system resulted in internal concentra— tions of parent cyanazine similar to that Observed in weed species. Cyanazine translocation was mainly acropetal from the point of application. Selectivity was not solely based on differential foliar uptake of cyanazine, but also on the preportion taken up by the foliage and roots. Under condi- tions favoring uptake by roots, the margin of selectivity may be reduced. The metabolism of cyanazine by corn, fall panicum, and green foxtail was compared to determine the contribu- tion of metabolism to selectivity. Cyanazine metabolism by plants with four leaves was examined following foliar or 14C-cyanazine. Parent material was root treatments with separated from metabolites by thin-layer chromatography. Five days following foliar application, 32.5 and 41.1% of a water-soluble metabolite were found in fall panicum and green foxtail, respectively. In corn two metabolites with Albert Dean Kern 19.1 and 25.7% of 140 activity were found in the water- soluble fraction. Only 12.0 and 6.2% of the same breakdown products were found in corn after a single day of treatment. Small quantities of other metabolites were also found. Metabolism of root-applied cyanazine appears to differ from foliar treatments in the weedy grasses as more parent cyana— zine was recovered. Green foxtail had equal amounts of un- altered cyanazine present in both shoot and root portions. The roots of corn and fall panicum contained less cyanazine than did the shoots. Rapid metabolism of cyanazine by corn roots provided evidence for an active detoxification mech- anism. Tolerance of greenhouse-grown corn to cyanazine and atrazine [2-chloro—4—(ethylamino)-6-(isopropylamino)-§f triazine] was compared when grown in Conover sandy loam soil. When preemergence and postemergence applications of cyana- zine were allowed to contact the soil, reductions in dry weight were Obtained under both low and high soil moisture conditions. SELECTIVITY OF CYANAZINE (2-[[4-CHLORO-6-(ETHYLAMINO)~§rTRIAZIN-2-YL] AMINO]-2—METHYLPROPIONITRILE) ON FALL PANICUM (RANIGUM DICHOTOMIFLORUM NIGHX.), GREEN FOXTAIL / (SETARIA VIRIDIS ‘.), AND CORN (ZEA MAYS L.) By Albert Dean Kern A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Crop and Soil Sciences 1974 ACKNOWLEDGMENTS The author wishes to express his sincere apprecia- tion to his major professor, Dr. William F. Meggitt, for his support and guidance throughout this study. Graditude is extended to Dr. Donald Penner for his guidance in the labor— atory and his constructive criticism in the preparation of this manuscript. The assistance of Dr. A. R. Putnam, Dr. M. J. Bukovac, Dr. E. C. Rossman, and Dr. M. J. Zabik as Guidance Committee members is gratefully acknowledged. The technical assistance of Mr. Ronald Stearns and Mr. RObert Bond is especially appreciated. Special thanks is given to my wife, Jan, for her patience and encouragement throughout the course of study. To those very special to me, Todd and Tara, my thanks for their unsuspecting sacrifices. ii LIST OF TABLES . LIST OF FIGURES. INTRODUCTION. TABLE OF CONTENTS CHAPTER 1: LITERATURE REVIEW . Fall Panicum.and the Nature of the Problem . Green Foxtail. . Fall Panicum and Green Foxtail Control Adjuvants for Herbicide Enhancement Effect of Time of Annual Grass Removal on Corn Yield Root and Foliar Absorption of Postemergence Herbicides. Cyanazine Action and Metabolism. CHAPTER 2: INFLUENCE OF STAGE OF GROWTH AND ADJUVANTS ON THE CONTROL OF FALL IN CORN WITH CYANAZINE . Abstract . . Introduction Materials and Methods Results and Discussion. Literature Cited. 0 iii PANICUM Page vii ODQWUUUUI-J 10 12 14 14 15 l7 19 31 CHAPTER 3: Abstract Introduction Materials and Methods Results and Discussion. Literature Cited. UPTAKE, MOVEMENT, AND METABOLISM IN PANICUM, GREEN EOXTAIL, AND CORN . 0 CHAPTER 4: CYANAZINE METABOLISM IN CORN, PANICUM, AND GREEN FOXTAIL Abstract Introduction Materials and Methods Results and Discussion. Literature Cited. _. CHAPTER 5: Abstract Introduction Materials and Methods Results and Discussion. Literature Cited. CHAPTER 6: LIST OF REFERENCES. APPENDICES FALL CORN TOLERANCE TO SOIL-APPLIED CYANAZINE. SUMMARY AND CONCLUSIONS iv Page FALL . . 33 . . 33 . 34 . . 35 . . 38 . 57 . . 59 . . 59 . . 60 . . 61 . . 6A . . 72 74 . 7A . 7A 76 77 . 87 . 88 91 . 98 LIST OF TABLES CHAPTER 2 1. Fall panicum control 3 and 7 weeks following postemergence herbicide treatments to three stages of growth, 1972 and 1973 . . . 2. Response of corn following postemergence herbicide treatments to corn with 3 to 4 leaves, 1972 and 1973. . . . . . . . . 3. Response of corn following postemergence herbicide treatments to corn with 4 to 5 leaves, 1972 and 1973. . . . . . . . 4. Response of corn following postemergence herbicide treatments to corn with 6 to 7 leaves, 1972 and 1973. . . . . . . . . 5. The effect of cyanazine on corn with 3 to 4 leaves as measured by plant height 3 and 7 weeks following treatment . . . . . . . 6. The effect of cyanazine and adjuvant additives on fall panicum control and corn injury, 1972 and 1973 . . . . . . . . . . . . . 7. Influence of adjuvants on cyanazine action on the dry weight of greenhouse- rown corn with 4 leaves and fall panicum with to 6 leaves. CHAPTER 3 1. Fresh weight of plants 9 to 11 days following foliar and foliar + root treatments of cyanazine to corn with 3 leaves and 6 to 7.5— cm fall panicum and green foxtail. . . . 2. lAC-cyanazine absorption by shoots of the seedlings of three species 1 and 5 days after foliar treatment . . . . . . . . . . Page 20 22 23 24 26 27 29 39 43 Page Metabolism from foliar lAC-cyanazine application to three species 1 and 5 days after treatment. . . . . . . . . . . 44 Distribution of activity in seedlings of three species 3 days after supplying the roots with C-CyanaZine o o o o o o o o o o 0 LI‘8 Metabolism from root application of 140- cyanazine to three species 3 days after treatment. . . . . . . . . . . . . 49 CHAPTER 4 l. 2. Thin-layer chromatography of 14C-cyanazine and metabolites. . . . . . . . . . . 65 ffircentage of recovered water-soluble forms of C-cyanazine l and 5 days after foliar treatment to three plant species . . . . . 66 Percentagiuof recovered chloroform-soluble forms of C-cyanazine l and 5 days after foliar treatment to three plant species. . . 67 Chromatography and percentage of total 14C recovered in the water-soluble fraction 3 days after supplying the roots of three species with C-cyanazine . . . . . . . 69 Chromatography and percentage of total 140 recovered in the chloroform-soluble frifition 3 days after supplying the roots with C- cyanazine. . . . . . . . . . . . . 70 CHAPTER 5 I. Effect of preemergence applications of cyanazine and atrazine to corn grown in the greenhouse under two moisture regimes . . . 78 Reduction in dry weight of corn harvested at three different stages of growth following preemergence treatments of cyanazine. . . . 80 Influence of atrazine and cyanazine on the growth of corn 10 days after soil treatment . 81 vi LIST OF FIGURES CHAPTER 3 1. Comparison of cyanazine phytotoxicity to corn and fall panicum 9 to 10 days following foliar treatment. . . . . . . . . . . . Absoflption of 14C_ —cyanazine and concentration C in three plant species 1 and 5 days following foliar treatment - - . - . Uptake and the concentration of cyanazine in the shoot and root portions of corn, fall panicum, and green foxtail seedlings which wEre grown in nutrient solution containing C-cyanazine . . . . . . . . . . . Translocation of lac-cyanazine in fall panicum and green foxtail . . . . . . . Translocation of lb’C-cyanazine in corn . . . CHAPTER 5 1. Relationship between the rate of cyanazine application and plant dry weight 10 days after treating corn with four leaves and maintained under low soil moisture conditions . . . . Relationship between the rate of cyanazine application and plant dry weight 10 days after treating corn with four leaves and maintained under low soil moisture conditions . . . . Response of corn to soil-applied postemergence treatments of cyanazine . . . . . . . vii Page 41 46 51 53 55 82 83 86 INTRODUCTION The elimination of undesirable plants is a problem in crop production. The annual losses from weeds plus the cost of their control in agriculture are great. Reduced crOp yield results from competition between crops and weeds for soil nutrients, space, water, 002, and light. Effective chemical weed control practices have aided farmers in in- creasing production. Of the many herbicides used, atrazine [2-chloro—4-(ethylamino)—6—(isopropylamino)—§7triazine] is one of the most widely used for selective weed control in corn (gea mays L.). Fall panicum (Panicum dichotomiflorum Michx.), an increasing annual grass weed prOblem, appears to be associ- ated with the continuous use of atrazine. The resistance of fall panicum to atrazine and the elimination of competing weed species during the growing season have provided the avenue for fall panicum invasion. Green foxtail (Setaria viridis L.), another annual grass, is moderately resistant to postemergence applications of atrazine. Although green foxtail has not become as serious as fall panicum, the threat of Michigan cornfields becoming infested with an— other grass species should be avoided. Failure of preemergence weed control in corn without effective postemergence control has resulted in reduced yields. Until recently, postemergence control of fall pan- icum and green foxtail was difficult. Cyanazine (2—[[4—chloro— 6-(ethylamino)-§ftriazin-2—yl]amino]—2-methylpropionitrile) offers an effective control measure for these grass weeds, although corn injury has been Observed with cyanazine. Examinations of cyanazine application rates and timeliness are needed to determine optimum levels for full season weed control to maximize corn yield. Age of corn, type of adjuvant, and environmental conditions appear to influence corn phyto- toxicity following cyanazine treatment in field trials. Cyanazine has only recently been registered for postemergence weed control in corn. Many factors which in- fluence crop phytotoxicity and annual grass control with cyanazine are not understood. The Objectives of this study were to (l) evaluate the performance of cyanazine and cyana— zine combinations as postemergence treatments for full- season fall panicum control, (2) determine the factors affect- ing corn tolerance and weed control at various stages of growth, (3) determine the extent of foliar penetration, translocation, and metabolism of cyanazine in corn and two weed species to determine the basis of selectivity. CHAPTER 1 LITERATURE REVIEW Fall Panicum.and the Nature of the PrOblem Fall panicum, a monocotyledonous plant, has recently become a serious weed prOblem in row crops (23, 24). It is an annual grass which can attain a height in excess of one meter, has an erect to decumbent or diffuse growth habit, and tillers profusely (20, 24, 56). It has glaborous sheaths and blades, with a ligule consisting of a dense ring of white hairs l to 2 mm long (78). The mature plant produces a pan- icle type inflorescence and is characterized by swollen nodes (20, 56, 79). The lower nodes of decumbent stems are often rooted (20, 46). This annual grass produces many seeds which can germinate throughout the growing season (24, 46, 56). A single fall panicum plant can produce up to 647 g of dry weight (56). Once established, fall panicum thrives well under a variety of soil conditions and reduces corn yield (24, 25, 32, 46, 47, 56, 80). Additionally, fall panicum is a nuisance at corn harvest. Recent reports and surveys have found fall panicum infestations in 23 North- eastern and corn belt states (2, 3, 21, 46, 52, 78, 79, 83). Recent practices of reduced tillage, earlier plant— ing dates, shorter cultivars, and the elimination of other weed species have encouraged fall panicum infestations (24, 46, 56, 71). In addition, the widespread use of atrazine for weed control in corn has allowed the atrazine— tolerant fall panicum to spread and flourish after competing species have been eliminated (2, 3, 21, 22, 46, 70). Many investigators have shown the ineffectiveness of atrazine as a preemergence or postemergence treatment to combat fall panicum (22, 23, 32, 47, 53, 80, 81). It has been hypothesized that the continuous use of atrazine killed susceptible strains of fall panicum, whereas, the population of tolerant strains survived and spread (23, 24, 71). Applications of hydroxy-atrazine, a breakdown product of atrazine, to fall panicum in the field and green- house raised speculation that repeated use of atrazine may have stimulated the growth of fall panicum (56). Other investigators suggested that the recent occurrence of fall panicum is due to the elimination of competing broadleaf and grass weeds over the last 10 to 15 years (23, 46, 56). Recently, atrazine—resistant redroot pigweed (Amaranthus retroflexus L.) and common groundsel (Senecio vulgaris L.) plant populations have been reported (49, 51, 72). Inherent physiological differences between two groundsel biotypes resulted in different responses to triazine herbicides (49, 51). The investigations were conducted on plants grown in nutrient solutions. The study suggested that resistance was not due to differences in plant exposure to the herbicides caused by variation in germination time, rooting depth, or morphology. The existence of other tol— erant species stimulated interest in the theory of survival of resistant strains to atrazine. However, fall panicum was the first weed species to emerge on soil treated with simazine [2-chloro-4,6-bis—(ethylamino)-§ftriazine] in 1957 and appeared tolerant to chloro—sftriazines (54). Fall panicum became the dominant species in cultivated fields following simazine and other isomers in other studies (6). These 1957 Observations were made one year before the release of triazines for commercial use. The concept of artificial selection to atrazine has 'been denied by a recent study on fall panicum plants taken from uncultivated fields (63). The researchers suggested that plants from populations never exposed to atrazine would be expected to be more susceptible to the herbicide than those from atrazine-treated fields. Results indicated that plants from both areas were equally tolerant to 4.5 kg/ha of atrazine. Green Foxtail Green foxtail is an annual grass that grows 30 to 90 cm tall. The growth habit is erect producing a dense panicle at maturity (20, 79). Green foxtail seedlings may 'be distinguished, although with difficulty, from other Setaria species by the glaborous upper leaf surface and the short hairs along the margin of the sheath. It differs anatomically from the closely related yellow foxtail [Setaria glauca (L.) Beauv.] in the lack of the several long, curly hairs at the base of the green foxtail leaf. Green foxtail is one of the most serious and widespread grass weeds (68, 79). Researchers have recommended the same herbicide control measure for both green and yellow foxtail (68, 83). While reports have shown that poor postemergence control of green foxtail was obtained with atrazine plus phytObland oil (42, 47, 68, 83), other studies revealed that green foxtail is more tolerant to atrazine than are some other Setaria species (33, 34, 35, 70). It has been the Observa- tion of the author that green foxtail is frequently associated with other annual grasses like witchgrass (Panicum capillare L.) or crabgrass [Digitaria sanguinalis (L.) Scop.] which are moderately tolerant to atrazine. In many cases, green foxtail has been the predominant weed present. Fall Panicum and Green Foxtail Control Preemergence treatments of cyanazine, simazine, ’butylate (sfethyl diisobutylthiocarbamate), and alachlor [2—chloro-2',6'-diethyl-fl¢(methoxymethyl) acetanilide] have been effective control measures for annual grass control in corn. Until recently, there has'been no effective post- emergence herbicide for fall panicum or green foxtail. Early postemergence treatments of atrazine plus alachlor resulted in a synergistic response on Japanese millet (Echinochloa crusgalli var. frumentacea) (1). These data suggested that early herbicide combination treatments may be candidates for removal of emerged fall panicum. Cyanazine, registered recently as a selective post— emergence treatment in corn, has resulted in good to excellent control of a wide variety of annual grasses. Unlike atrazine, cyanazine has a short-term soil residue with no carry-over to successive crops (82) and controls the atrazine-tolerant species (26, 32, 33, 34, 76, 83). The short residual life in the soil has been measured under a number of artificial and field situations. Treatments of cyanazine at 2.2 kg/ha failed to show toxicity to oats (Avena sativa L.) seeded with- in 10 weeks after application (26). A similar study resulted in no soybean [Glycine max (L.) Merr.] injury or reduction in yield when planted 4 to 6 weeks after a 3.4 kg/ha cyana- zine treatment (30). An Illinois study indicated that soy— beans could be planted as a rescue crop following the fail- ure of cyanazine-treated corn (76). Three soil residue studies using instrumental and bioassay analysis indicated that cyanazine was less persistant than atrazine or sima- zine in all tested soil types (19, 44, 69). Cyanazine degradation in soils resulted in the loss of one-half of the initial activity in 1.3 to 5 weeks (9). The rate was great— er under moist conditions. Although fall panicum and green foxtail are suscept- ible to postemergence treatments of cyanazine, little infor— mation is available concerning efficacy of the herbicide on various growth stages of the annual grasses. Corn injury has occasionally been Observed following cyanazine treatments. Cyanazine at 3.4 kg/ha resulted in slight injury to corn in the 3 and 4—leaf stage (29). Cyanazine plus phytObland oil resulted in additional crop injury in several trials, espec- ially when applied to older corn (29, 32, 42). Adjuvants for Herbicide Enhancement Incomplete wetting and spreading of water-herbicide solutions on waxy leaves of weeds may result in poor control. Numerous studies have shown that the addition of a phyto— 'bland oil to atrazine resulted in greater weed control with- out losing selectivity to the crop (l5, 18, 28, 39, 55, 67, 85). The purpose of adjuvants in a postemergence herbicidal spray is to provide a spreading action, solubilizing the cuticle, and to keep the leaf surface moist longer, allow- ing increased foliar penetration and absorption (4, 15, 62, 84). Studies using luC—atrazine revealed greater herbicide uptake when oil additives were used in the water solution (4, 55, 62). The increased activity of the foliar sprays may permit herbicide rates to be reduced. The effective rate of atrazine 4.2 kg/ha with water was comparable to 2.8 kg/ha when 9.4 L of phytobland oil was added (28, 39). Many other herbicides which are applied postemergence call for the use of a surfactant or oil adjuvant (82). Some of these herbicides demand special types of surfactants because of their composition (39, 84). Recent interest in the use of phytobland oils from an agricultural origin has provided an alternative to the petroleum oils. Nalewaja (43) suggested that "the use of replenishable crop origin oils in place of nonreplenishable petroleum oils should be encouraged to help preserve our fossil fuels for tasks in which they are essential". Lin— seed oil and sunflower oil were compared to various adju- vants for the effectiveness of atrazine on green and yellow foxtail control (41, 42, 67). The vegetable oils and petroleum oils were superior to the surfactants. Similar weed control results have been reported when phytObland vegetable oils were added to cyanazine (42, 43). The add- ition of linseed oil significantly enhanced luC-dicamba (3,6-dichloro-ofanisic acid) uptake by leafy spurge (Euphorbia esula L.) and resulted in greater control of yellow foxtail with dalapon (2,2-dichloropropionic acid). Although phytotoxicity data with cyanazine plus vegetable oil were not conclusive, another study showed less sugar beet (Beta vulgaris L.) injury with phenmedipham (methyl- mfhydroxycarbanilate—mfmethylcarbanilate) plus linseed or sunflower oils (40). Effect of Time of Annual Grass Removal on Corn Yield Bell and Koeppe (7) demonstrated that allelopathy (noncompetitive influence) plus competition of giant fox- tail (Setaria faberii Herm.) reduced corn growth in the greenhouse. The researchers suggested that the interfer- ence of crop growth resulting from the release of phytotoxic substances from the grass plants plays a similar role under field conditions. lO Bunting and Ludwig (l3) removed weeds from corn at 3, 4, and 6 weeks after emergence. Two to four-week per- iods of competition during the early growth stages of corn were sufficient to reduce grain yield. Similar studies revealed that sorghum [Sorghum bicolor (L.) Moench.] yields were significantly reduced when weeds were not removed for 4 to 8 weeks after planting (l4). Knake and Slife (37) found that corn yield were reduced only slightly by early season competition over a 3-year study. Reductions in yield occurred when competition was not eliminated until the giant foxtail was greater than 23 cm in height. Giant foxtail left to maturity resulted in only a 12.5% average yield reduction. Others (18, 55) found that corn yields were reduced when atrazine plus oil treatments were delayed until the late growth stages (5 to 10 cm) of yellow foxtail and barnyardgrass [Echinochloa crusgalli (L.) Beauv.] growth. Root and Foliar Absorption of Postemergence Herbicides Several investigators have noted the influence of root uptake of atrazine for maximum weed kill following postemergence treatments (36, 42, 55, 73, 74, 75). Studies at Cornell University indicated that non-foliar uptake appears to play a major role in herbicide uptake of early postemergence treatments (1). Elimination of root uptake of atrazine by seedling Japanese millet reduced control by four to six-fold. Thompson and Slife (74) found that root absorption of atrazine applied postemergence to small ll 'broadleaf weeds is not a requisite for their control. How- ever, greater giant foxtail control was Obtained when root uptake supplemented the foliar uptake from an over—the—top spray (73). Phytotoxicity of atrazine on yellow and green fox- tail was greater under high moisture conditions when spray treatments were applied to both soil and foliage (55). Atrazine treatments applied to giant foxtail on dry soil followed by no rainfall reduced dry weight, but did not reduce the stand (73). In another study, the researchers (75) reported that corn seedlings treated with atrazine and grown under cold, wet conditions were injured. They con- cluded that low temperatures decreased the rate of detoxi- fication to peptide conjugates from foliarly-absorbed atra- zine in the stressed plants. The data showed the presence of dihydroxybenzoxazin-3—one and hydroxy-atrazine in the roots which indicates root uptake. However, the researchers reported that the effect of the reduced amount of benzoxazinone under these conditions did not contribute to the death of the corn. Timing the applications of postemergence treatments to young annual grass weeds was required for effective con- trol (28, 36, 55, 85). Late season green foxtail control with 2.2 kg/ha of cyanazine was greater than with cyanazine at 0.6 kg/ha with oil (42). Nalewaja suggested that the residue in the soil resulted in effective kill of late germinating seeds. Excellent control was obtained when 12 applications were made to annual grasses 1.5 to 4.0 cm high. Later treatments to 5 to lo-cm grass resulted in poor con- trol. Some short weeds escaped control when under the canopy of taller treated weeds (28). Additionally, the lack of residual cyanazine under dense weed conditions after treatment may allow new weeds to emerge. Cyanazine Action and Metabolism Cyanazine is readily absorbed by plant foliage; and when applied to the soil, it is absorbed by the roots and translocated to the leaves (82). It is a photosynthetic inhibitor which interfers with the "Hill reaction". The chemical moves acropetally to the Site of action via the apoplast toward areas of highest transpiration. Cyanazine at 171 ppm is five times more soluble in water at 25 C than is atrazine. Availability of this herbicide for plant up— take via the soil depends upon the total amount of water present and the adsorption characteristics of the soil for cyanazine (26, 82). Cyanazine rate adjustments vary from 1.1 kg/ha on a sandy soil with little organic matter to 4.5 kg/ha on a clay soil with 4% organic matter to achieve satisfactory weed control from preemergence applications. Cyanazine differs from atrazine by the presence of a nitrile group which appears to be more easily attacked than the chlorine atom (8, 9, 10, 12, 82). Degradation involves removal of the ethyl group, hydration of the cyano group, and the exchange of the chlorine with a hydroxyl 13 group (10, ll, l2, 16, 27). Evidence for conjugation of cyanazine with peptides has been reported as a possible detoxification mechanism (10, ll, 12, 76). Although con- jugation detoxification mechanisms with cyanazine are not fully understood, glutathione conjugation of atrazine has been reported to be a major detoxification mechanism in corn (57, 59, 61, 70, 71). In corn plants, hydrolytic and dealkylation reac— tions detoxify cyanazine; however, in soils, large amounts of dealkylated products are formed (10). While hydroxy- cyanazine was not detected in corn, a hydroxy-acid [2- hydroxy-4-(l-carboxy—l-methylethylamino)-6—(ethylamino) —1,3,5-triazine] was found in corn sap 22 hr after treat— ment. A dealkylated hydroxy-acid [2-hydroxy—4-(l-carboxy- l-methylethylamino)—6—amino-1,3,5—triazine] was also found 14 in large quantities in corn grown in C-cyanazine treated soils. Both of these hydroxy compounds were found to have non-herbicidal properties (12). Degradation products found in wheat (Triticum vulgare L.) and potatoes (Solanum tubersum L.) were similar to those found in corn (11). However, wheat leaves contained significant amounts of the chloro-acids which only occurred in the roots of corn. CHAPTER 2 INFLUENCE OF STAGE OF GROWTH AND ADJUVANTS ON THE CONTROL OF FALL PANICUM IN CORN WITH CYANAZINE Abstract The response of corn (Zea mays L.) and fall panicum (Panicum dichotomiflorum Michx.) to postemergence herbicide applications at three stages of growth was examined. Early postemergence application of cyanazine (2-[[4-chloro-6- (ethylamino)js-triazin-2-yl]amino]—2-methy1propionitrile) at 3.4 kg/ha provided the best control with minimum crop injury and greatest corn yield. A reduction of 25% in corn yield resulted when fall panicum was removed by hand at the 7 to 8—leaf stage as compared to removal of plants with 2 leaves. The addition of various adjuvants increased cyana- zine action on both fall panicum and corn in field and greenhouse experiments; however, field trials showed no differences in grain yield at harvest. In the greenhouse, less corn injury was observed with a vegetable oil additive than with other adjuvants. 14 15 Introduction Fall panicum is increasing as a weed prOblem in many areas of the United States (ll, l2, l3, 17). The occurrence of this annual grass appears to be associated with the continuous use of atrazine [2—chloro-4-(ethylamino)— 6-(isoprOpylamino)-§;triazine]. Fall panicum is tolerant to applications of atrazine, detoxifying it by conjugation with peptides (l2, 13, 15, 16, 18). Tolerance of fall panicum to atrazine and the elimina— tion of other competing weed species during the growing season has provided an avenue for ecological change in the corn field. When allowed to grow without competition, fall panicum plants tiller profusely producing large numbers of seed to infest the area.1 Insufficient preemergence control of fall panicum without effective postemergence control results in reduced corn yields. This late germinating grass must be controlled for the entire season to maximize corn yield. Corn yields are not reduced if weeds are removed during the early growth stage of the crop (1, 2, 6, 7, 14). Since fall panicum lSerdy, F. S. 1973. The effect of competition, herbicides, and ethylene on germination, growth, and development of fall panicum. Ph. D. Thesis. The Pennsyl- vania State University, University Park. 77 PP. 16 is capable of metabolizing cyanazine2 or simazine [2—chloro— 4,6-bis(ethylamino)-§ftriazine] (5, 15), control may be achieved using postemergence applications of these Chemicals. Addition of nonphytotoxic petroleum oils or phytObland oils increased herbicidal activity of cyanazine (4, 8, 9, 10), 'but resulted in crOp injury and at present are not recommend- ed for use with cyanazine. Kapusta (4) suggested that cyana— zine application made prior to the fifth leaf stage of corn provided maximum selectivity. The purpose of this research was to examine various postemergence herbicide treatments for fall panicum control in corn. The study was designed to determine the tolerance of corn and the control of fall panicum when cyanazine was applied at various growth stages. In addition, the experi- ment was conducted to determine the competition between corn and fall panicum and the extent of yield losses it caused when left for various periods of time. The efficacy and selectivity of cyanazine with various adjuvants were examined. 2Thompson, R. P. and F. w. Slife. 1973. Uptake and degradation of inc-Bladex and lLLC—atrazine by four crop and two weed species. Weed Sci. Soc. Abstr. No. 142. 17 Materials and Methods Field studies during 1972 and 1973 were conducted on soils heavily infested with fall panicum. Plots were 3.1 by 12.2 m in 1972 and 3.1 by 15.2 m in 1973 and con— sisted of four corn rows per plot. The herbicides were applied with a tractor-mounted sprayer at 2.11 kg/cm2 pressure delivering 215 L/ha. All treatments were replicat- ed four times. Fall panicum control and corn injury were visually rated on a O to 10 scale, with 0 representing no control or injury and 10 representing complete kill. Corn injury was also measured by dry weight, plant height, and grain yields. Plant height measurements were taken 3 and 7 weeks following treatment by measuring the height of the tallest hanging leaf. The average of ten random measure- ments per plot determined the plot mean. Additionally, 3 m of the center two rows were harvested 3 weeks following treatment for dry weight determination in one study. The remaining center two rows were harvested at maturity and grain weights corrected to 15.5% moisture. The first field experiment was designed to evaluate the performance of various herbicide treatments on fall panicum and corn over three stages of plant growth. After disking, the field was planted with a no-till planter with rows 1 m apart. The area was planted to 'Teweles 80' corn on May 19, 1972 and May 18, 1973. The plots were arranged in split-plot design. Herbicide applications were made on June 2, 13, and 22, 1972 and June 7, 14, and 22, 1973. At 18 treatment time fall panicum was at the 2 to 3, 4 to 5, and 7 to 8-leaf stage and corn at the 3 to 4, 4 to 5, and 6 to 7-leaf stage. The corn was sidedressed with 134 kg/ha N during the study. Soil was a sandy clay loam with 2.0% organic matter. Another experiment was designed to evaluate the effect of various adjuvants on cyanazine toxicity to weeds and corn. Experimental procedures were similar to the preceding study. The sandy loam soil contained 2.4% organic matter. Early postemergence treatments were applied to fall panicum with three leaves and corn with four leaves. Greenhouse experiments were used to supplement the adjuvant field study. Corn and fall panicum were grown in 946-ml containers filled with sandy clay loam soil contain- ing 2.5% organic matter. Corn and fall panicum were treated in the 4 and 4 to 6-leaf stage, respectively. The plants were grown under 23 to 27 C with supplemental lighting of 12.9 klux during a 16 hr day. Pots were watered daily with Hoagland's no. 1 solution (3). A phytObland crop oil,3 3Sun 11E is a phytobland oil produced by Sun Oil Company, Philadelphia, Pennsylvania. l9 6 an oil concentrateu, a surfactantS, and a vegetable oil were compared. The plants were harvested 9 days following treatment and the dry weights Obtained. Data presented are the means for two experiments both containing five replica— tions. Results and Discussion Response of fall panicum and corn following herbicide treat» ment at three stages of growth. Evaluation several weeks after application indicated that the herbicide applications gave the greatest fall panicum control when applied to the 2 to 3-leaf stage (Table 1). Variation in fall panicum_ control existed between years with the late treatment stage. Shorter and less dense fall panicum at the late stage treat— ment in 1973 could have resulted in greater plant coverage and soil interception of cyanazine. b, Agri-oil plus is a blend of surfactant and paraf- finic oil produced by Gordon's Chemicals, Kansas City, Kansas. 5 Citowett is a surfactant containing alkylaryl polyglycol ether produced by BASF Wyandotte Corporation, Parsippany, New Jersey. Bio-Veg is an emulsified vegetable oil produced 'by Barzen of Minneapolis, Inc., Minneapolis, Minnesota. 2C) .Hoapcoo opoamaoonoa maoapcoo ocuoaw m0 0.0 mm mi m.m m6 0.0 0.0 m.m ma a.a ma aa.m+m.m+a.a wwmswsaam + 8832 aao + l. 0.0 m6 mi Tm 0.m .. ma m.a 0.m mm mm aa.m+m.m+a.a .aoasesa.mw + 08383 m.m ma m.a Sm m.m mm mm mm mm m.m m.m 0.0a aa.m+m.m aao + mfinsfiao 3. 0.0 :6 m3 mm mm .. ma ma 0.m m.m mm a:.m+a.a aao + 85.388 m.m o.a ma 9: m.a o.a ma mm m6 m.a o..m o.m Hm Ocammqmao mm 0.0 0.0 m.a a.m m.a m.m m.a m6 0.: m6 m.m m.m mfissssao 0.0a 0.0a 0.0a 0.0a 0.0a 0.0a 0.0a 0.0a 0.0a 0.0a 0.0a 0.0a .. aoapsoo 8803 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 .. aospsoo 883 mama mama mama mama mama mama mama mama mama mama mama mama 8&wa psoapsmse m 0p a : Op m m 0p m m op a : op m m 0p m spam owmpm mama mmmpm mama quapma Moms Gm>mw mmcapma Moms OOHQB .mama 08s mama .Spsoam mo mowmpm omanp Op mpcmapmmap muaoappon mocmwaoampmom wdazoaaom mxooz a was m aoaunoolesoaswm aamm "H magma 21 Cyanazine plus crop oil at 2.2 kg + 9.4 L/ha re- sulted in greater fall panicum control than did cyanazine alone at 3.4 kg/ha at all treatment dates. Although cyana— zine plus oil at 1.7 kg + 9.4 L/ha gave similar control as cyanazine at 3.4 kg/ha, eventually the remaining herbicide in the soil was inadequate for control of late season ger- minating grass seeds. Greater control was obtained with early application of cyanazine plus alachlor during the 1973 season. The fall panicum was nearer to the 2—1eaf stage in 1973 and nearer to the 3—leaf stage in 1972. De- sired fall panicum control was not obtained with atrazine plus simazine plus oil. Cyanazine alone did not injure corn with 3 to 5 leaves. Reduced grain yields in 1973 were the result of ineffective fall panicum control (Tables 2, 3, and 4). The addition of a nonphytotoxic crop oil or alachlor plus crop oil reduced crop vigor 3 weeks following treatment in 1972. A decrease in dry weight was not measured in 1973. While no rainfall accompanied the 2—day period following the treatments in 1973, rainfall amounting to 0.7 cm, 3.9 cm, and 0.5 cm fell during the 2-day period following the 1972 applications. The increased injury in the 1972 season may have resulted from additional wetting and a modified cuticle which aided in penetration. Allowing fall panicum competition to persist until corn had 6 to 7 leaves reduced corn yields by 25% (Tables 2 and 4). Herbicide injury combined with weed competition 22 .mzoa 03p mavwas mgp mo mampma m Sosa 00pmm>amg Cams mpcmam 039 .pcmspmmap wcazoaaoa mammz m 0mpmm>amg mm: goao mo pgwamz mamo .aaax mpmamsoo H OH mmsSmca on u 00 .9008 mwcmm mamapasz mlcmoczm m0 a0>0a mm 03p 90 pamammmao mapcmoaaacwam poc mam mamppma amaaaam mp Umzoaaom measaoo canvas 030020 00 aam: 0n 0.m :.0 0 mmaa 00_a.a 0.0 a:.m+m.m+a.a WMMNMSam + 0sas0sp< aao + 0 mmom on :.m :.0 0 ammm 00 m.a m.0 a:.m+m.m+a.a s0a200a0 + 0dan000a0 00 00:m 00 0.: m.0 0 m:mm 0 m.a m.: a:.m+m.m aao + 0san000a0 on 00m: n0 0.: m.0 0 mamm 0 :.m m.0 a:.m+a.a aao + 0dan000a0 00 aomm 00 0.: m.0 00 m:00 n0 0.m m.0 :.m 0sane00m0 n 0:m: 0 a.m 0.0 0 0am0 0 :.m m.0 m.m 0sas000a0 0 :mom 00 m.: 0.0 0 0mm0 0 m.m 0.0 -- aosscoe 000002 0 mmm 00 0.: 0.0 0 mamm 0 m.m 0.0 -- aospsoe a0003 A0£\wxv Apcmag\awv A0£\mxv Apcmam\fimv a0g\mxa caoam opnwamz gmchma camah opcwamz nwcapma 0pmm pcmEpmmaH gamma mam madmca Camaw ham maSmcH mama mama .mama 000 mama .00>00a m 0s m Eva: magmam Op magmapmmap mcaoanamn mocmwamempmom wcHzoaaoa ano mo mwmo 00m .m magma 23 .mzoa osp oauwaa 03p ao mampmfi m Sosa aummbamg mams mpcmam 038 .pcmapmmap msasoaaom mxmmz m 00pmm>a0£ 003 moao mo pgwamz mamo .aaax mpmagEoo H OH mmasmca on n on .pmme mwcmm mamapasz m.:0025Q mp am>0a mm 03p p0 pcmammaao mapcmoamacwam pom 0am mamppma amaaSam an Umzoaaom mQESHOO Canpaz mammzm 0 m00: 00 m.0 a.0 0 ammo 00 :.m m.0 a:.m+m.m+a.a wwmamsam + 0sas0sa< aao + n 0ma: 0 m.m m.0 0 0am: 0 m.m m.m a:.m+m.m+a.a seasosas + 0dan000a0 00 mamm n0 m.0 0.a 00 maam 0 m.m m.m a:.m+m.m aao + 0dan000a0 0.:mm: n0 a.a m.0 0 0mmm 00 m.m 0.a a:.m+a.a aao + 0san0s0a0 0 0:mm 0 0.m 0.0 00 mamm 0n0 m.m 0.0 :.m 0san000a0 00_mam: 00 m.m 0.0 00 a:m0 on m.: 0.0 m.m 0san000a0 0 aamm 0 a.m 0.0 0 mmam 0 m.0 0.0 -- aosssoe 000003 0 mmaa on.m.0 0.0 0 :mom n0 :.0 0.0 -- aosssoo a0002 Assxmav Asaaaa\s01 Aas\0sv Asaaaa\s01 Aes\0sv camah opgwamz nwchma camam Opgwamz nmchms mpmm pcmepmmaa Camaw mam mMSmcH madam mam madmca mama mama .mama 000 mama .00>00a m 0s : Spas pcsam Op mpcmapmmap mcaoanams 00C0mamempmom wcazoaaom choc mo mmcommmm .m magma 24 0s03 mpS0am 0:9 .pc0Sp00sp wcazoaaos pc0s0ssa0 mapcmoasacwam p0: 0s0 ms0pp0a .mzos 03p 0a00aS 0gp mo 0s0p0S m Sosa 00p00>s0g 0M003 m 00pm0>s0£ 003 goso so pswa03 msmo .aaax 0p0aQSoo H OH mmssmca on u o D .pm0e 0w20m 0amapa52 m_smossm m0 a0>0a mm 0gp p0 smaaSam m0 003oaaos mQSSHOO Gaspaz mc0020 00 0mmm 000.m.aa 0.a 0 amom 0 :.ma 0.0 a:.m+m.m+a.a MWMNMSam + 0das0sp< HHO + -- -- -- 0 aa:m 00 m.a 0.m a:.m+m.m+a.a scanssas + 0sas000a0 00 mmmm 0 0.aa m.: 00 ma:m 00 a.a m.m a:.m+m.m aao + 0dan000s0 -- -- -- 00 ammm 0 m.a m.: a:.m+a.a aao + 00a0000s0 0 m:m: 00 m.ma m.0 0 mm:m 00 m.0a 0.a :.m 0das000s0 onvammm 000.0.aa :.a 0 m:0: 00 m.aa m.0 m.m 0can000S0 0 m:©: 0 :.ma 0.0 o amm: 0 m.ma 0.0 In aospcoo 000003 0 mmma 000 0.ma 0.0 00 mmmm 0 0.ma 0.0 -- aosssoa s000s Ass\0sv Asasaa\s00 10s\0sv Asseaa\s00 Ass\0sv 0a0am opswa03 hwcapms 0a0am opswa03 nwcapms 0p0m pc0Sp00sB Samsw msm msSWSH camsw msm msSWCH mama mama w Spas mpcmag op mpc0Sp00sp 00a0aps0£ 0oc0ws0S0pmog waszoaaos csoo so 0mcomm0m 0.mama 000 mama .00>00a a 0p .: 0a90s 25 eliminates the feasibility of treating 6 to 7-leaf corn infested with 7 to 8-leaf fall panicum. Full season fall panicum control is required for maximum yields (Tables 1 and 2). This can be accomplished by applying cyanazine or cyanazine plus 011 prior to the time fall panicum has 4 leaves and corn has 6 leaves. Plant height was employed as a measure of corn re- sponse following treatments at the early stage of growth (Table 5). Measurements taken 3 and 7 weeks after treat- ment indicate the ability of corn to compensate for early injury. Comparing effective treatments, no reduction in corn height was Observed following cyanazine at 3.4 kg/ha or cyanazine plus oil at 2.2 kg + 9.4 L/ha. However, crop damage was reflected in the 1972 grain yields from cyana- zine plus oil at 2.2 kg + 9.4 L/ha. With the exception of the 3-week measurement in 1973, plant height differences were not observed with cyanazine plus alachlor plus oil or atrazine plus simazine plus oil. Some yield reduction was obtained in plots receiving these treatments due to either excessive crop injury or erratic long season fall panicum control. Comparison of adjuvants on cyanazine action. The addition of several adjuvants to cyanazine improved fall panicum control (Table 6). Adjuvants added to 2.2 kg/ha of cyana- zine resulted in Similar or greater control than the 3.4 kg/ha rate alone. The nonphytotoxic crop oil and oil concentrate resulted in greater weed control and more 26 00s so 000a msa0000 sop so psaoa p00smas 00p 0p s0s00 0s0s 0ps000s0000: .poam s0s mpc0S0s5000S OH so 000s0>0 0gp 0ps0m0ss0s c00S pc0Sp00ss .mpcmas Ian .pmma 0wS0m 0asapasz 0_qmocsa m0 a0>0a mm 0gp p0 ps0s0s usa0 mapcmoasacwsm pos 0s0 0s0pp0a smaaSam mn.00zoaaos mSSSHOo manpaz mammzm ens m:a 00 mm 000 aaa 00 am a:.m+m.m+a.a aao + 00a00Sa0 + 0sanssp< 00 mma 00 mm 000_aaa 00 mm a:.m+m.m+a.a aao + s0a000a0 + 0san000s0 0 mma 00 am 000 maa 0 mm a:.m+m.m aao + 0sas000S0 00 ama 00 a: 00 mma 00 0m a:.m+a.a aao + 00a0000a0 0 :ma 00 :: 00 mma 00 mm :.m 0sansssa0 00 0ma 0 0: 00 a0a 00_mm m.m 0dan000s0 00 mma 0 w: 0 mma 00 mm nu Hospmoo 000003 0 am 00 d: 0 :m 0 :m In aospcoo m000z as as as as $80 0x003 a 0M003 m 0M003 a 0M003 m 0p0m pc0Sp00ss mama mama npsma0s pssaa 0.pc0Sp00sp wcazoaaos 0x003 a 020 m pcwa0£ mpcmas m0.00s5000S 00 m0>00a : Op m Spa: csoo co 0cammcmm0 so po0ss0 0S9 .m 0a00B 27 .aaax 0p0amSoo H OH mmsSnca so HospsOo on u on .p00s 0wc0m masapasz 0_c00csm hp a0>0a mm 0gp p0 pC0s0ssa0 mapcmoasacwam pos 0s0 0s0pp0a smaaaam m0.003oaaos 0QS5aoo QHSpH3 020020 00 0mmm p 0a0m 0.0 0.a m.a 0.0 0.0 0.a a:.m+m.m+a.a aao + 0sasssa0 + 0sas0sp¢ 0 mamm p mmmm a.0 m.a a.m :.0 0.m m.m a:.m+m.m+a.a aao + seagusas + 0sas000so 00 mamm -- m.0 .. a.a -- m.m -- am.m+m.m aao 0an0p000> + 0sassssso op :::m n mmam m.0 m.0 a.a m.: m.m 0.a am.a+m.m psspo0ss50 + 0sas00030 00 00mm 0 mmmm 0.0 0.: :.a 0.0 m.m 0.0a am.m+m.m .0000 aao + 0sassssao on 0mmm p mamm 0.0 m.a a.m :.m m.m 0.m a:.m+m.m aao + 00asss0a0 00 mam0 0 m:00 0.0 0.0 m.a m.a a.m 0.m :.m 0sassssso p mmom p a00m 0.0 m.0 m.m m.: m.a a.0 m.m 0sasasaao 00 :m00 0 0a:0 0.0 0.0 0.0a 0.0a 0.0a 0.0a .. aospsoo 000003 0 mam 0 amwm 0.0 0.0 0.0 0.0 0.0 0.0 .. aospdoo s0002 asnxmav A00\0xv A00\0sv mama mama mama mama mama mama mama mama 0p00 ps0Sp00ss 0a0am Camsw passhsa Ssoo 3003 a 3003 m paospcoo Snowflam Hams 0.mama 0S0 mama «mHSwdH Qsoo 0:0 aospcoo afloaqms aaws so 00>apa000 p00>5000 000 0sammsmmo so po0ss0 039 .m 0a909 28 severe corn injury than did the surfactant or vegetable 011. Although crop injury was observed initially, final grain yields were not significantly reduced with any adjuvant- herbicide combination. Cyanazine plus alachlor plus oil provided good control with the exception of the infestation late in 1972. Atrazine plus simazine plus 011 more effec- tively controlled fall panicum in this experiment than in the stage of growth study; however, more corn injury also was observed. The adjuvant treatments were also examined in the greenhouse on corn with 4 leaves and fall panicum plants with 4 to 6 leaves. Application of 2.2 kg/ha of cyanazine caused injury (Table 7). Less corn injury resulted from the cyanazine and the cyanazine plus vegetable oil treat- ment compared to cyanazine plus other adjuvants; however, erratic control of the fall panicum occurred. Crop oil, oil concentrate, and surfactant appeared to enhance corn injury and grass control. In the greenhouse, addition of the sur- factant resulted in fall panicum death in contrast to Sim— ilar treatments in the field. These data indicate that the use of a phytObland additive increased both fall panicum control and corn injury. The degree of selectivity did not appear to be broadened. Although corn treated with cyanazine plus oil or alachlor plus oil usually resulted in yields comparable to the hand- weeded controls, the use of cyanazine alone appears con— sistently less injurious. Cyanazine at 3.4 kg/ha applied 29 Table 7. Influence of adjuvants on cyanazine action on the dry weight of greenhouse—grown corn with 4 leaves and fall panicum with 4 to 6 leaves. Dry weighta Cyanazine Adjuvant Rate Corn Fall panicum (kg/ha) (L/ha) (mg/3 plants) (mg/cup) 0.0 None -- 301 a 470 a 2.2 None -- 248 bc 197 b 2.2 Oil 9.4 226 c 103 b 2.2 Oil conc. 2.3 217 c 118 b 2.2 Surfactant 1.2 221 c 0 c 2.2 Veg. oil 2.3 263 b 174 b aMeans within columns followed by similar letters are not significantly different at the 5% level by Duncan's Multiple Range Test. 30 to the early stages of plant growth (corn with less than 5 leaves and fall panicum with less than 4 leaves) eliminated competing fall panicum and provided sufficient soil residual for long season control and maximum yields. By the late treatment, the fall panicum had tillered to form a dense foliage and resulted in unacceptable weed control. In addition, increased corn injury suggests late season treat- ments should not be used. 10. 11. 12. 31 Literature Cited Bunting, E. S. and J. W. Ludwig. 1964. Plants compe- tition and weed control in maize. Seventh Brit. Weed Contr. Conf. Proc. 1:385-388. Burnside, 0. C. and G. A. Wicks. 1967. The effect of weed removal treatments on sorghum growth. Weeds 15:204-207. Hoagland, D. R. and D. I. Arnon. 1950. The water culture method for growing plants without soil. California Agr. Exp. Sta. Circ. 347. 32 pp. Kapusta, G. 1970. Corn growth stage tolerance to post-emergence applied SD-l5418. Proc. N. Cent. Weed Contr. Conf. 25:32-33. Kern, A. D., w. F. Meggitt, and D. Penner. 1974. Uptake, movement, and metabolism of cyanazine in fall panicum, green foxtail, and corn. Weed Sci. 22:(In preparation). Knake, E. L. and F. N. Slife. 1969. Effect of time of giant foxtail removal from corn and soybeans. Weed Sci. 17:281-283. Knake, E. L. and F. N. Slife. 1965. Giant foxtail seeded at various times in corn and soybeans. Weeds 13:331-334. Miller, S. D. and J. D. Nalewaja. 1973. Effect of additives upon phenmedipham for weed control in sugar beets. Weed Sci. 21:67-70. Nalewaja, J. D. 1972. Linseed oil and postemergence herbicides. Proc. Flax Institute of the U. S. 42:10-14. Nalewaja, J. D., J. Pudelko, and B. Skopiec. 1973. Influence of oil additives on foxtail control with cyanazine. Proc. N. Cent. Weed Contr. Conf. 28:79. Parochetti, J. V. 1970. The ten worst weeds of field crops: Panicums. Crops and Soils 22:12—14. Parochetti, J. V. 1974. Yellow nutsedge, giant green foxtail, and fall panicum control in corn. Weed l3. 14. 15. 16. 17. 18. 32 Schnappinger, M. 0., Jr. and H. P. Wilson. 1972. Ratios of atrazine and simazine for the control of fall panicum in corn. Proc. Northeast. Weed Sci. Soc. 27:4-9. Staniforth, D. W. 1957. Effects of annual grass weeds on the yield of corn. Agron. J. 49:55l~555. Thompson, L., Jr. 1972. Metabolism of chloro—Sf triazine herbicides by Panicum and Setaria. Weed Sci. 20:584-587. Thompson, L., Jr., J. M. Houghton, F. W. Slife, and H. S. Butler. 1971. Metabolism of atrazine by fall panicum and large crabgrass. Weed Sci. 19:409-412. b. S. Department of Agriculture, Agricultural Research Service. 1968. Extent and cost of weed control with herbicides and an evaluation of important weeds, 1965. ABS 34-102. 85 pp. Jengris, J. 1973. Fall panicum control in field corn in Massachusetts 1972. Proc. Northeast. Weed Contr. Conf. 27:52-55. CHAPTER 3 UPTAKE, MOVEMENT, AND METABOLISM OF CYANAZINE IN FALL PANICUM, GREEN FOXTAIL, AND CORN Abstract Greenhouse studies indicated that root absorption after postemergence applications of cyanazine (2-[E4—chloro- 6-(ethylamino)—§7triazin-2—yl]amino]-2-methylpropionitrile) enhanced phytotoxicity to fall panicum (Panicum dichotomi- florum Michx.), green foxtail (Setaria viridis L.), and corn (22a mays L.). Less 14C-cyanazine was taken up by the foliage of corn than by the weed species. A lower concen- tration of parent cyanazine in corn leaves was also evident. The addition of a phytObland oil to the treatment solution resulted in increased foliar cyanazine absorption 1 and 5 days following treatment. Although rapid metabolism occurred in corn roots, the large amounts of cyanazine absorbed via the root system resulted in internal concentrations of parent cyanazine similar to that Observed in the weed species. Cyanazine translocation was mainly acropetal from the point of application. The basis of selectivity is not solely 'based on the differential foliar uptake of cyanazine, but also on the proportion taken up by the foliage and roots. Under conditions favoring uptake by roots, the margin of selectivity may be reduced. 33 34 Introduction Until recently, selective postemergence herbicides have been ineffective on fall panicum and green foxtail (8, ll, l3, 14). Although green foxtail is less tolerant to triazine herbicides than fall panicum, the threat of corn- fields invaded with another weedy grass should be avoided. Cyanazine offers a possible control measure for these weedy grasses (8). The influence of the microclimatic conditions on the foliar uptake of atrazine is well documented. Investi— gators have shown an increase in atrazine or cyanazine activity due to high relative humidity, increased tempera— ture, and the presence of additives (5, 10, 12, l5, 16). Other researchers have suggested the importance of soil interception of atrazine resulting in root uptake to obtain optimum control of annual grasses (7, 8, 9, 10, 11, l2, 15, 16). In a field trial in 1972 on a sandy loam soil, Signi- ficant reductions in corn growth were observed following cyanazine plus oil treatments.:L Rain amounting to 7.8 cm fell for 11 of the 15 days following treatment. Conditions favorable for greater root absorption by green foxtail and corn resulted in additional phytotoxicity. lKern, A. D., W. F. Meggitt, and R. 0. Bond. 1972. Green foxtail control in Northern Michigan. N. Cent. Weed Contr. Conf. Res. Rep. 29:144. 35 The Objectivies of this study were to determine the contribution of foliar and root absorption to cyanazine toxicity and to determine the role that translocation and metabolism play in selectivity. Materials and Methods Fall panicum and green foxtail seeds, collected in Michigan, were planted in 473—ml cups and allowed to grow 6 to 7 cm in height. 'Michigan 396' corn seed was planted in 946-ml cups and allowed to attain the 4—leaf stage. The grasses and corn were grown in the greenhouse and thinned to 15 plants and 3 plants per cup, respectively. Treatments designed to cover only the foliage were accomplished by placing a 0.8 to 1.0-cm layer of vermiculite on the soil to intercept the herbicide spray. After the treated foliage had dried, the vermiculite was removed. In the foliage plus root treatments the spray was allowed to contact soil and foliage. Treatments were made with 235 L/ha at 2.1 kg/cm2 pressure and a phytObland oil2 at 4% (v/v) or 9.4 L/ha was added. The treatments were assigned in a completely randomized design. The plants were harvested 9 days following treatment and fresh weights were measured. Data reported are the means of two experiments with four replications each. 2Sun 11E is a phytobland oil produced by the Sun 011 Company, Philadelphia, Pennsylvania. 36 Foliar application of lb’C—cyanazine. To Obtain optimum cuticular wax deposition, fall panicum, green foxtail, and corn were grown outdoors during the spring and summer months. Plants of fall panicum and green foxtail at the 4 to 5-leaf stage and corn in the 4-leaf stage were brought l4C_ to the laboratory and selected for uniformity for the cyanazine absorption and translocation study. A 5—ul drop containing 0.1 nCi of 14C—cyanazine was placed inside a lanolin enclosure on the second leaf of corn. Similar droplets were applied between two lanolin bars placed per- pendicular to the length of the grass leaves. The ring- labeled 14C-cyanazine had a specific activity of 3.86 nCi/nM 3 and was 97% pure. Following treatment, the plants were moved to a growth chamber with a l6-hr day and a light in— tensity of 19 klux. Day temperature was maintained at 25 C and night temperature at 22 C. The plants were supplied with a modified Hoagland's no. 1 solution (6) and random- ized daily. The treatments were replicated three times and the experiments were repeated. After 1 and 5 days, the treated plants were sec- tioned into three parts. The treated leaf acropetal to the point of application was removed and immediately placed into a freezer at -5 0. Similarly, the rest of the aerial 3 luC—labeled cyanazine was supplied by Shell Development Company, Modesto, California. 37 plant portion basipetal to the spot and the root portion were separated and frozen. The plant portions were homo- genated in a Sorvall Omni-Mixer for 2 min in 10 ml of 80% methanol, and the homogenate was filtered through glass wool as suggested by Beynon et_al. (2, 3, 4). Following reextraction the residue was collected for dry weight and methanol-insoluble residue analysis by the Schoniger com- bustion method (17). The volume of the methanol-soluble filtrate was reduced in_yagug and 10 ml of water added. The aqueous fraction was partitioned with chloroform. The volumes of the fractions were reduced in_vagug_and 500 p1 of cold methanol added. Aliquots of 50 p1 were assayed by liquid scintillation spectrometry. Another 200 p1 were spotted onto 250 nm thick (20 by 20 cm) silica gel F-254 (Brinkmann Instruments) thin layer chromatography (TLC) plates. The aqueous fractions were developed in ethyl acetatezH20:formic acid (70:4:4, v/v/v) and then radio- autographed. The lipophylic fractions were developed in acetonezchloroform (35:65, v/v). The radioactive spots on the TLC plate were removed and radioassayed by liquid scintillation spectrometry. The scintillation solution consisted of 0.1 g of dimethyl POPOP [1,44bis 2-(4-methyl- 5-phenyloxazolyl)—benzene], 5.0 g of PPO (2,5—diphenyloxazole), 50.1 g of naphthalene, 380 ml of toluene, 380 m1 of 1,4- dioxane, and 240 ml of absolute ethanol. Root uptake of lLAG-cyanazine. The plant species were ger- minated in the greenhouse in a sand medium and transferred 38 to a Hoagland's no. 1 solution containing 5,uCi/L of 14C- cyanazine (cyanazine concentration was 3.5 x 10“7 m). Based on previous Observations of root weights, volumes of solu- tion were adjusted to 10 mls for the weed plants and 200 ml for corn. The plants were allowed to remain in the l4C_ labeled solution for 3 days. The plants were then removed, and the roots were washed in three consecutive water baths. The harvested material was frozen as previously described prior to analysis. At harvest two plants from all previous treatments were quickly frozen with dry ice, freeze-dried, and radioautographed. Results and Discussion In greenhouse studies, green foxtail was more sensi- tive to cyanazine than was fall panicum. Significant re- ductions in fresh weight of the three species indicate the importance of root uptake on cyanazine phytoxicity (Table 1). Although the addition of a phytObland oil masked the signi- ficance of root uptake in fall panicum, a marked response was shown at the 2.2 and 3.4 kg/ha rate. Increased corn injury due to soil interception was observed with cyanazine at 3.4 kg and cyanazine plus 011 at 2.2 kg and 3.4 kg + 9.4 L/ha (Figure l). Foliar application of lLAC-cyanazine. Fall panicum absorbed 3 to 5 times as much 14C—cyanazine from foliar application than did green foxtail. Corn leaves took up only about 35 and 20% as much labeled herbicide at l and 5 days, 39 .a0>0a mm p0 pS0oasaswa0 0a Soap0oaass0 so 0ogp0S sos 05a0> s 9 .p003 0mq0m 0asapafiz 0_S0osdm mn.a0>0a mm 0gp p0 pc0s0ssa0 maps00asacwa0 pos 0s0 0s0pp0a s0aaSa0 £pa3 00ao0s0 QHSpa3 0Q0020 m.a m.m 0.m 0.m 0.ma m.ma 03002 .. u- -- -- 0 m.m s0 0.aa :.m :.m 0 0.0 0 m.a 0 :.0 00 m.a 00 m.m 0 :.ma :.m m.m 00 a.0 o m.a o a.0 00_:.a s0 m.0a s0 a.aa :.m a.a I: In 0 m.0 n 0.m 00 m.:a 00 0.aa 0.0 :.m 00 m.0 00 m.a on m.a 0 m.m 000.0.ma 00 m.aa 0.0 m.m 000 0.0 p m.m 0 :.m 0 0.: 00.m.ma p0 a.aa 0.0 a.a 0 0.a 0 a.m 0 a.m 0 m.m 0 :.ma 0 m.ma 0.0 0.0 AQSO\SwV AQSO\SmV A0ps0as m\SmV A0S\av A0S\wxv poos + poos + poos + aao 00am0c0mo s0aaos s0aaos s0aaos s0aaos s0aaos s0aaos aa0pxos c00s0 S50ac0s aa0s Qsoo psma03 £00ss 0.aa0pxos S00sm 0S0 S50ac0s aa0s Soum.a Op 0 0c0 00>00a m £pa3 Ssoo Op 0mam0c0mo so 0pS0Sp00sp poos + s0aaos 0S0 s0aaos wca3oaaos 0300 Ha Op m 0pc0as so pgma03 £00ss .a 0a00s Figure 1. 40 Comparison of cyanazine phytotoxicity to corn and fall panicum 9 to 10 days following foliar treatment. The plants on the left of each plate are the controls. The center plants received only foliage treatments. The soil and foliage of the cup on the right were both allowed to intercept the herbicide spray. (A) Corn treated with 2.2 kg plus 9.4 L/ha of cyanazine plus oil. (B) Fall panicum treated with 3.4 kg/ha of cyanazine. 41 /cvnnnzms+ OIL CHECK FOLIAR _ qvnnazme .1 ‘ \QBK SOIL B CHECK FOLIAR FOHAR 42 respectively, as green foxtail and about 5% as much as fall panicum (Table 2). However, after 5 days a significant in- crease in absorption resulted from the addition of the phytObland oil. This may be the reason for foliar injury observed in the field following postemergence applications of cyanazine plus 011. Oil increased uptake of cyanazine two-fold in fall panicum and four—fold in green foxtail. Following foliar 14C-cyanazine applications, the percentage of parent material remaining among the three species was not distinguishably different at l and 5 days (Table 3). Less unaltered lLLC-cyanazine was recovered at the 5-day harvest in all three species. The nature of the metabolism appears to be different among the species. Corn harvested 5 days following treatment had more distinguish- able metabolites than did fall panicum or green foxtail. The origin in the separation system included some breakdown products; however, they were not further separated. Fall panicum contained a metabolite in the aqueous fraction which moved only Slightly from the origin and could not be separated from it. Greater absorption and less metabolism accounted for the high concentration of parent cyanazine in fall panicum both 1 and 5 days following foliar treatment (Figure 2). Less absorption and a lower concentration of unaltered cyanazine in corn appeared to be the basis for selectivity to foliar treatments. Root uptake of luC-cyanazine. Corn absorbed more l[LC-- cyanazine than fall panicum and green foxtail when l4 43 Table 2. C-cyanazine absorption by shoots of the seedlings of three species 1 and 5 days after foliar treat- ment.a luC-uptake . Treatment Without With SPECIES Duration oil oil (daTS) (dpm/ms) (dpm/ms) Fall panicum 1 13,525 bcd 24,463 a 5 . 14,588'bc. 35,979 a Mean 14,056 30,174 Green foxtail 1 2,311 e 9,794 bcd 5 4,725 cd 17,484 b Mean 3,518 13,639 Corn 1 827 e 730 e 5 805 e 3,865 cd Mean 816 2,298 aMeans followed by similar letters are not signifi- cantly different at the 5% level by Duncan's Multiple Range Test. b 5% level. F value for oil vs. no oil is Significant at the 44 Table 3. Metabolism from foliar 14C—cyanazine application to three species 1 and 5 days after treatment.a Percentage of total 140 recovered Methanol- Species Parent Origin Metabolites insol. (7») W (%) (%) 1 day Fall panicum 66.6 a 22.9 ab 9.2 cd 1.4 ab Green foxtail 64.9 a 31.5 a 2.4 de 0.0'b Corn 73.2 a 15.9 be 9.9 cd 0.7 ab 5 day Fall panicum 47.9 ab 38.0 a 13.5 bc 0.5 ab Green foxtail 40.1 b 37.3 a 22.6 b 0.0 b Corn 40.8 b 25.4 a 30.5 a 3.3 a aMeans within columns with Similar letters are not significantly different at the 5% level by Duncan's Multiple Range Test. Figure 2. 45 Afisorption of 14C—cyanazine and concentration of C in three plant species 1 and 5 days follow- ing foliar treatment. The height of the total bar represents the total accumulation and the darkened portion within the bar indicates the amount of unaltered parent cyanazine. 46 232° s‘" x 9w mma Green Corn Fall Foxtail Panicum 47 transferred to a nutrient solution containing the labeled cyanazine (Table 4). Fall panicum had the highest percent- age of parent cyanazine in the shoots and corn the lowest (Table 5). Although large amounts of radioactivity were found in corn roots compared to other species (Table 4), much more was metabolized (Table 5). Green foxtail roots contained large amounts of unaltered cyanazine. This could explain the greater sensitivity of green foxtail than fall panicum to cyanazine. Fall panicum roots altered cyanazine to products other than parent cyanazine and contained a large amount of methanol-insoluble residue. Although a large amount of cyanazine was metabolized, a loss in the margin of selectivity resulted from root treatments to the plants in the 4-leaf stage (Figure 3). It should be noted that corn plants took up 40 times more nutrient solution than fall panicum or green foxtail plants. As a result, more herbicide uptake and translocation would likely occur. Translocation studies. Cyanazine was rapidly translocated in fall panicum, green foxtail, and corn following foliar applications (Figures 4 and 5). When a phytObland oil was added, greater cyanazine movement was Observed (Figure 4). In all plants, 14 0 moved acropetally in the treated leaf with minimal basipetal movement. Root uptake studies indi- cate uniform translocation acropetally from roots to areas of highest transpiration. The translocation pattern of cyanazine is consistent with other sftriazine herbicides. 48 Table 4. DiStribution of activity in seedlings of three Egecies 3 days after supplying the roots with C-cyanazine.a 140 distribution Species Shoot Root ( dpm/ms ) ( dpm/ms ) Fall panicum 331 a 387 ab Green foxtail 560 ab 500 ab Corn 900 b 2020 c aMeans followed by similar letters are not signifi- cantly different at the 5% level by Duncan's Multiple Range Test. 49 Table 5. Metabolism from root application of 14C—cyana— zine to three species 3 days after treatment.a Percentage of total 140 recovered Methanol- Species Parent Origin Metabolites insol. (%) (72) (%) (%) Shoot Fall panicum 73.8 a 19.8 be 0.0 cd 6.4 cd Green foxtail 61.6 ab 18.5 be 2.5 c 17.2 bc Corn 53.8 b 7.1 d 21.6 b 17.4 bc Root Fall panicum 28.6 c 33.7 a 0.0 cd 37.6 a Green foxtail 57.2 ab 21.0 ab 0.0 cd 21.8 ab Corn 9.2 d 21.6 ab 58.4 a 10.8 c aMeans within columns followed by similar letter are not significantly different at the 5% level by Duncan's Multiple Range Test. 50 Uptake and the concentration of cyanazine in the Shoot and root portions of corn, fall panicum and green foxtail seedlings which were grown in nutrient solution containing 4C—cyanazine. Figure 3. 51 :35... E5252. 500. .32.... :0... .N.— .v« .9— .0.— .ON :0! X 9" mma Figure 4. 52 Translocation of lLAC—cyanazine in fall panicum and green foxtail. The treated plants (A) and corresponding radioautograph (B) Show fall panicum and green foxtail 5 days following a foliar treatment with cyanazine. Each set of grass species have the cyanazine treatment (left) compared to cyanazine plus oil (right). The treated plants (C) and corresponding radioauto- graph (D) Show fall panicum and green foxtail 3 days following lacement in a nutrient solu-_ tion containing 1 C-cyanazine. Figure 5. 5LL l4 Translocation of C-cyanazine in corn. The treated plants (A) and corresponding radioauto- graph (B) Show corn treated for a 5—day duration with cyanazine (left) compared to cyanazine plus oil (right). The treated plants (C) and corre— sponding radioautograph (D) Show acropetal move- ment 5 days after supplying the oots with 140- cyanazine (left) and leaf with C-cyanazine plus 011 (right). 55 .. 56 Phytotoxicity following postemergence application of cyanazine was the result of both foliar and root absorp- tion. In relation to the weed species, corn absorbed less 140 material from foliar applications and more from root treatment. Slower inactivation of cyanazine by fall pani- cum and green foxtail appears to play a role in selectivity following root treatments. However, selectivity is not solely based on foliar uptake, but also on the proportion taken up by foliage and roots. Under conditions favorable for root uptake the margin of selectivity may be reduced. U'l 10. 11. 57 Literature Cited Beynon, K. I., P. Bosio, and E. E. Elgar. 1972. The analysis of crOps and soils for the triazine herbi— cide cyanazine and some of its de radation products. II. Results. Pestic. Sci. 3:401- 08. Beynon, K. I., G. Stoydin, and A. N. Wright. 1972. A comparison of the breakdown of the triazine herbicides cyanazine, atrazine and simazine in soils and in maize. Pestic. Biochem. and Physiol. 2:153-161. Beynon, K. I., G. Stoydin, and A. N. Wright. 1972. The breakdown of the triazine herbicide cyanazine in soils and maize. Pestic. Sci. 3:293-305. Beynon, K. I., G. Stoydin, and A. N. Wright. 1972. The breakdown of the triazine herbicide cyanazine in wheat and potatoes grown under indoor conditions in treated soil. Pestic. Sci. 3 379-387. Dexter, A. 0., 0. C. Burnside, and T. L. Lavy. 1966. Factors influencing the phytotoxicity of foliar applications of atrazine. Weeds 14:222-228. Hoagland, D. R. and D. I. Arnon. 1950. The water culture method for growing plants without soil. California Agr. Exp. Sta. Circ. 347. 32 pp. Kapusta, G. 1970. Corn growth stage tolerance to post-emergence applied SD—l5418. Proc. N. Cent. Weed Contr. Conf. 25:32-33. Kern, A. D. and W. F. Meggitt. 1972. Fall panicum control in corn with postemergence herbicide treat- ments. Proc. N. Cent. Weed Contr. Conf. 27:20. Nalewaja, J. D. 1972. Linseed oil and postemergence herbicides. Proc. Flax Institute of the U. S. 42:10-14. Nalewaja, J. D., J. Pudelko, and B. Skopiec. 1973. Influence of oil additives on foxtail control with cyanazine. Proc. N. Cent. Weed Contr. Conf. 28:79. Parochetti, J. V. 1974. Yellow nutsedge, giant green foxtail, and fall panicum control in corn. Weed Sci. 22:80-82. 12. 13. 14. 15. 16. 17. 58 Smith, C. N. Jr. and J. D. Nalewaja. 1972. Uptake and translocation of foliarly- applied atrazine. Weed Sci. 20: 36— 40. Thompson, L., Jr. 1972. Metabolism of chloro~ ~s- triazine herbicides by Panicum and Setaria. IWeed Sci. 20: 584— 587. ‘—" “"— Thompson, L., Jr., J. M. Houghton, F. W. Slife, and H. S. Butler. 1971. Metabolism of atrazine by fall panicum and large crabgrass. Weed Sci. 19: 409- 412. Thompson, L., Jr. and F. W. Slife. 1969. Foliar and root absorption of atrazine applied postemergence to giant foxtail. Weed Sci. 17:251-256. Thompson, L., Jr. and F. W. Slife, and H. S. Butler. 1970. Environmental influence on the tolerance of corn to atrazine. Weed Sci. 18:509-514. Wang, C. H. and D. L. Willis. 1965. Radiotracer Methodology in Biological Science. Prentice-Hall Inc., Englewood Cliffs, New Jersey} 363 pp. CHAPTER 4 CYANAZINE METABOLISM IN CORN, FALL PANICUM, AND GREEN FOXTAIL Abstract The metabolism of cyanazine (2-[[4-chloro-6— (ethylamino)ag-triazin-2—yl]amino]—2-methylpr0pionitrile by corn (Zea mays L.), fall panicum (Panicum dichotomiflorum Michx.), and green foxtail (Setaria viridis L.) was com- pared to determine the contribution of metabolism to selec- tivity. Cyanazine metabolism by plants with 4 leaves was examined following foliar or root treatments with 140- cyanazine. Parent material was separated from metabolites ”by thin-layer chromatography. Five days following foliar application, 32.5 and 41.1% of a water—soluble metabolite were found in fall pan- icum and green foxtail, respectively. In corn two metabo- lites with 19.1 and 25.7% of 140 activity were found in the water-soluble fraction. Only 12.0 and 6.2% of the same ‘breakdown products were found in corn after a single day of treatment. Small quantities of other metabolites were also found. Metabolism of root-applied cyanazine appears to differ from foliar treatments in the weedy grasses as more parent cyanazine was recovered. Green foxtail had 59 60 equal amounts (61.1 and 57.2%) of unaltered cyanazine pre- sent in both shoot and root portions. The roots of corn and fall panicum contained 78 and 60% less cyanazine, re- spectively, than did the shoots. Rapid metabolism of cyana— zine by corn roots provided evidence for an active detoxi- fication mechanism. Introduction Fall panicum can metabolize atrazine [2-chloro-4- (ethylamino)-6-(isopropylamino)-§ftriazine], a widely used corn herbicide, to peptide conjugates (16, 17). Green fox- tail also has a greater tolerance to atrazine than other species in the same genus (ll, 16). Similar studies indi— cate that the two species could not significantly detoxify simazine [2—chloro—4,6-bis-(ethylamino)-§ftriazine] or cyanazinel (ll, 16). In addition to dealkylation, the pri- mary pathways responsible for the resistance of corn to atrazine are glutathione conjugation in Shoots and hydrolytic reactions in the roots due to benzoxazinone (3, 12, 13, 16, 17). It has been suggested that dealkylation to less toxic metabolites are more evident in plants that are susceptible to triazine herbicides (l4). lThompson, R. P. and F. N. Slife. 1973. Uptake and degradation of lLAC—Bladex and 14C-atrazine by four crop and two weed Species. Weed Sci. Soc. Abstr. No. 142. 61 Corn grown in cyanazine treated soil for 32 and 70 days contained chlorotriazines and hydroxytriazines includ- ing the dealkylated derivatives (3, 5). Cyanazine applied to corn sap was hydrolyzed resulting in loss of the nitrile group but showed no evidence of glutathione or cysteine conjugation. The researchers concluded that 2-hydroxy-4— (1-carboxy-1-methylethy1amino)-6-ethyl-amino-1,3,5-triazine was a direct breakdown product from cyanazine during the incubation. They also suggested that the extracted amide- cyanazine from corn plants was a result of uptake of that compound from the soil. Similar products were found in wheat (Triticum aestivum L.) and potatoes (Solanum tuberosum L.) as in corn. However, wheat leaves contained significant amounts of the chloro acids which otherwise only occurred in the roots of corn (5). The purpose of this study was to determine the nature of differences in cyanazine metabolism between corn and the susceptible fall panicum and green foxtail. The significance of root and foliar degradation pathways com— pared within each species were also of interest. Materials and Methods Fall panicum, green foxtail, and corn seeds were germinated in the greenhouse, after which the seedlings were grown outside. Fall panicum and green foxtail plants with 4 to 5 leaves and corn with 4 leaves were selected and brought to the laboratory for l[AC—cyanazine treatment. A 62 5au1 drop containing 0.1 uCi of lac-cyanazine was placed inside a lanolin enclosure on the second leaf of corn. DrOp- lets were placed between two 1anolin'bars on the second leaf of the weed species. A 4% phytObland oilQ-water solution was used as the carrier. The uniformly ring-labeled 140- cyanazine had a specific activity of 3.86,uCi/nM and was 97% pure.3 Following treatment, plants were moved to a growth chamber with a 16-hr day at 25 C and a light intensity of 19 klux. Night temperatures were 22 C. The plants were supplied with a modified Hoagland's no. 1 solution (8) and randomized daily. After 1 and 5 days, the treated plants were sec— tioned into three parts. The treated leaf acrOpetal to the point of application was removed and immediately placed into a freezer at —5 C (1). Similarly, the rest of the aerial plant portion basipetal to the Spot and the root portion were separated and frozen. The plant portions were homogenated in a Sorvall Omni—Mixer for 2 min in 10 ml of 80% methanol, and the homogenate filtered through glass wool as suggested by Beynon 23.213 (3, 4, 5). The volume of the methanol-soluble filtrate was reduced in vacuo and 2Sun 11E phytObland oil is produced by Sun 011 Company, Philadelphia, Pennsylvania. 3 lLLC-labeled cyanazine was supplied by Shell Devel- opment Company, Modesto, California. 53 10 m1 of water added. The aqueous fraction was partitioned with chloroform. The volumes of the fractions were reduced in zagug and 500 pl of cold methanol added. Aliquots of 200 pl were spotted onto 250 nm thick (20 by 20 cm) silica gel F-254 (Brinkmann Instruments) thin—layer chromatography (TLC) plates. The aqueous fractions were developed in ethyl acetatezH20:formic acid (70:4:4, v/v/V) and then radioautographed. The lipOphylic fractions were developed in acetonezchloroform (35:65, v/v). The radioactive spots on the TLC plate were removed and radioassayed by liquid scintillation spectrometry. The scintillation solution used consisted of 0.1 g of dimethyl POPOP [194-21372’(4‘ methyl-5-phenyloxazolyl)-benzene], 5.0 g of PPO (2,5- diphenyloxazole), 50.1 g of naphthalene, 380 m1 of toluene, 380 ml of 1,4-dioxane, and 240 ml of absolute ethanol. The activity in each spot was calculated as the percent of total activity from the TLC plate. Percentage data were trans- formed to arc sin for statistical analysis. Metabolites were identified by comparing Rf's to published Rf's in cyanazine degradation schemes (1, 2, 3, 4, 5, 6, 7, 9). The plants for the root uptake studies were germin- ated in the greenhouse in a sand medium and transferred to a Hoagland's no. 1 solution containing 5,pCi/L of 140- cyanazine (cyanazine concentration was 3.5 x 10'7 M). iased on previous Observations of root weights, volumes of solu— tion were adjusted to 10 ml for the weed plants and 200 ml for corn. The plants were allowed to remain in the 64 lITO-labeled solution for 3 days. The plants were then re- moved and the roots were washed in three consecutive water baths. The harvested material was frozen prior to analysis. Data reported are the means for two experiments with three replications. Results and Discussion The distribution of metabolites following develop— ment in thin-layer chromatographic (TLC) systems is shown in Table 1. A number of distinguishable metabolites (A to 0) were compared to cyanazine breakdown products as identi- fied by Beynon §t_al, (3, 4, 5). Five compounds in trace or small amounts (B, D, E, F, N) were located by the TLC ”system, but could not be compared to other published Rf values (7, 9). Thin-layer chromatographs of the water— soluble fractions indicated that a difference in the nature of metabolism of foliarly applied cyanazine existed between corn and the weed species 1 and 5 days after treatment (Table 2). Following foliar treatments, corn appeared to metabolize cyanazine to near equal ratios of the stable products A and C. In contrast, fall panicum and green fox— tail metabolism resulted in a large percentage of A. The percent of stable product increased over time in all species. Similar percentages of parent cyanazine were found in the three species 1 and 5 days after foliar treatment (Table 3). The large percentage of J in green foxtail indicated a dealkylated product. The Rf values did not reveal the 65 Table 1. Thin-layer chromatography and structures of 140- cyanazine and metabolites. R' NA N R3HN L 2— NHR2 N Rf Group structuresa Methanol- Chloroform— Compound soluble soluble reference R1 R2 R3 System Ib System IIc Cyanazine Cl C(CH3)20N 02H5 .98 .80 A A OH C(CH3)2COOH H .00 .00 B .04 -- C 0H C(CH3)2000H C2H5 .08 -- D .10 -- E .13 -_ F .18 -- G OH H 02H5 .27 -- H OH H H .36 -- I 01 C(CH3)2000H C2H5 .83 -— Cl C CH3 2CONH2 H J C1 C(CH3)20N H .90 .65 K C1 C(CH3)200NH2 C2H5 .93 .32 L OH C(CH3)2CN 02H5 —- .05 M Cl 0(CH3)2CONH2 C2H5 -- .13 N -— .18 0 C1 H C2H5 -- .55 aStructures taken from Beynon gt_al, (4). ‘bSystem I is ethyl acetate-HQO-formic acid (70:4:4). CSystem II is acetone-chloroform (35:65). 66 Table 2. Percentage of recovered water-soluble forms of 140— cyanazine 1 and 5 days after foliar treatment to three plant species. Percentage of total 14C recovered from TLC plate Fall Green Corn panicum foxtail C d L t. 1 d 5 d 1 d 5 d l d 5 d ompoun 0730011 08)” 08>”y (W 03W 0‘3”" 07 A .00 12.0 19.1 19.9 32.5 34.5 41.1 B .04 6.6 4.7 2.2 5.5 2.3 3.4 C .08 6.2 25.7 0.5 3.0 -- 1.6 D .10 -- —- 0.6 1.7 1.1 -- E .13 -- tra -- -— -— -- F .18 -— -— 1.5 -- -- 0.6 G .27 —- tr 1.2 tr —- -- J .90 -— -- -- 0.9 —- -- K .93 -- -- -— -- -— 0.3 Cyanazine .98 0.6 —- 1.4 1.5 1.3 3.7 atr = trace 67 Table 3. ffircentage of recovered chloroform-soluble forms of C-cyanazine l and 5 days after foliar treatment to three plant species. 14 Percentage of total C recovered from TLC plate Fall Green Corn panicum foxtail Compound Location 1 day 5 day 1 day 5 day 1 day 5 day (Rf) (%) (%) (%) (%) (%) (%) A .00 0.6 7.4 1.0 4.9 1.8 1.1 L .05 -- -- tra 0.5 -- 0.3 M .13 -— -- tr tr -- 0.4 N .18 -- -- -- -- 0.4 1.0 K .32 -- -- 0.9 0.7 1.4 -— 0 .55 —— 0.4 0.3 -- 4.5 -- J .65 -- —- -- —— -- 12.9 Cyanazine .98 73.2 40.8 62.5 45.2 55.7 36.4 atr = trace 68 presence of J in fall panicum. A larger number of metabo- lites were found in the weed species than in corn. The susceptibility of the annual grasses to cyanazine may be due to this difference in metabolism to the stable products. Supplying the roots with 14C-cyanazine failed to produce significant recoverable amounts of the stable pro— duct A in the shoots of corn as compared to foliar 140- cyanazine application (Table 4). However, large amounts of A and C were found in the corn roots. This suggests a very active detoxification mechanism in the root system. In contrast, all recovered radioactivity in the water- soluble fraction of fall panicum and green foxtail was com- pound A. Small amounts of the dealkylated cyanazine J were found in the chloroform fraction in green foxtail (Table 5). The percentage of parent material in the shoot portion was comparable among the three species. However, the roots of corn and fall panicum contained less cyanazine than did the shoots. Green foxtail had large amounts of unaltered cyana- zine present in both shoot and root portions. As previously reported this may be the reason for the increased sensiti— vity of green foxtail to cyanazine (10). The occurrence Of the dealkylated hydroxy-acid in the weed species supports the report that dealkylation reactions are more evident in triazine-susceptible plants (14). Although breakdown of cyanazine occurred over the time of l to 5 days, the data suggested that a difference in metabolism among the three Species was not the sole 69 Table 4. Chromatography and percentage of total 14C recov- ered in the water-soluble fraction 3 days I ter supplying the roots of three species with C- cyanazine. 14 Percentage of total C recovered from TLC plate Fall Green Corn panicum foxtail Compound Location Shoot Root Shoot Root Shoot Root (Rf) (%) (%) (%) (%) (7») (%) A .00 7.1 17.6 -- 30.4 14.5 12.3 B .04 4.4 9.8 -— -- -- -— C .08 19.8 39.4 -- —— __ __ E .13 tra tr tr -- -- -- F .18 tr -- -- -- -- -- G .27 tr -— —- —- —— -— I .83 -— 0.6 -- —- —- -- J .90 tr —- -- -- -- -- K .93 0.8 —— -- —- -- —- Cyanazine .98 0.8 -- -- -— -- -— atr = trace 7O Table 5. Chromatography and percentage of total 140 recov- ered in the chloroform-soluble {fiaction 3 days after supplying the roots with C-cyanazine. 4 Percentage of total 1 C recovered from TLC plate Fall Green Corn panicum foxtail Compound Location Shoot Root Shoot Root Shoot Root (Rf) (%) (%) (7o) (%) (%) (%) A .00 1.3 3.7 -- 0.4 tra tr M .13 __ 0.8 -- -_ -- -— N .18 -- 0.9 —- -- -- ~- 0 .55 0.6 -- -- -- -- —- J .65 0.1 —- -- -— 1.6 7.0 Cyanazine .98 53.7 9.7 73.6 28.6 61.6 57.2 a tr = trace 71 'basis for selectivity from foliar treatments. However, rapid metabolism of cyanazine by roots of corn and fall panicum reveals an active detoxification mechanism in the roots of these species. Greater sensitivity of green fox- tail to cyanazine may relate to its inability to alter the parent compound. It appeared that sufficient amounts of root-applied cyanazine reached the site of action in fall panicum to provide effective kill. 10. 72 Literature Cited Beynon, K. I. 1972. The analysis of crOps and soils for the triazine herbicide cyanazine and some of it degradation products. I. Development of method. Pestic. Sci. 3:389-400. Beynon, K. I., P. Bosio, and K. E. Elgar. 1972. The analysis of crops and soils for the triazine herbi- cide cyanazine and some of its degradation products 11. Results. Pestic. Sci. 3:401-408. Beynon, K. I., G. Stoydin, and A. N. Wright. 1972. A comparison of the breakdown of the triazine herb- icides cyanazine, atrazine and simazine in soils agd in maize. Pestic. Biochem. and Physiol. 2:153- l 1. Beynon, K. I., G. Stoydin, and A. N. Wright. 1972. The breakdown of the triazine herbicide cyanazine in soils and maize. Pestic. Sci. 3:392-305. Beynon, K. I., G. Stoydin, and A. N. Wright. 1972. The breakdown of the triazine herbicide cyanazine in wheat and potatoes grown under indoor conditions in treated soils. Pestic. Sci. 3:379-387. Brown, N. P. H., C. G. L. Furmidge, and B. T. Grayson. 1972. Hydrolysis of the triazine herbicide cyana- zine. Pestic. Sci. 3:669—678. Crayford, F. V. and D. H. Hutson. 1972. The metabolism of the herbicide, 2-chloro-4-(ethylamino)-6-(l—cyano- l-methylamino)-S-triazine in the rat. Pestic. Biochem. and Physiol. 2f295-307. Hoagland, D. R. and D. I. Arnon. 1950. The water culture method for growing plants without soil. California Agr. Exp. Sta. Circ. 347. 32 pp. Hutson, D., E. C. Hoadley, M. H. Griffiths, and C. Donninger. 1970. Mercaptic acid formation in the metabolism of 2-chloro-4-ethylamino-6—(l-methyl- 1-cyanoethylamino)—S—triazine in the rat. J. Agr. Food Chem. 18:507-5I2. Kern, A. D., W. F. Meggitt, and D. Penner. 1974. Uptake, movement, and metabolism of cyanazine in fall panicum, green foxtail, and corn. Weed Sci. 22:(In preparation). 11. 12. 13. 14. 15. 16. 17. 18. 73 Oliver, L. R. and M. M. Schreiber. 1971. Differential selectivitg of herbicides on six Setaria taxa. Weed Shimabukuro, R. H. 1967. Atrazine metabolism and herbi— cidal selectivity. Plant Physiol. 42:1269-1276. Shimabukuro, R. H. 1968. Atrazine metabolism in re- sistant corn and sorghum. Plant Physiol. 43:1925- 1930. Shimabukuro, R. H. 1967. Significance of atrazine dealkylation in root and shoot of pea plants. J. Agr. Food Chem. 15:557-562. Shimabukuro, R. H., H. R. Swanson, and W. C. Walsh. 1970. Glutathione conjugation: Atrazine detoxifi— cation mechanism in corn. Plant Physiol. 46:103-107. Thompson, L., Jr. 1972. Metabolism of chloro-s- triazine herbicides by Panicum and Setaria. Weed Sci. 20:584-587. “"‘—" "“"" Thompson, L., Jr., J. M. Houghton, F. W. Slife, and H. S. Butler. 1971. Metabolism of atrazine by fall panicum and large crabgrass. Weed Sci. 19:409-412. Thompson, L., Jr. and F. W. Slife. 1969. Foliar and root absorption of atrazine applied postemergence to giant foxtail. Weed Sci. 17:251—256. CHAPTER 5 CORN TOLERANCE TO SOIL-APPLIED CYANAZINE Abstract Tolerance of greenhouse-grown corn (Zea mays L.) to cyanazine (2-[[4-chlorO-6-(ethylamino)-§7triazin-2-y1]amino] -2-methylpropionitrile) and atrazine [2-chloro-4-(ethyl- amino)-6—(isopropylamino)—§ftriazine] were compared when grown in Conover sandy loam soil. Reductions in dry weight were obtained following preemergence applications and post- emergence applications of cyanazine allowed to contact the soil, under both low and high soil moisture conditions. Results of this study indicate that corn tolerance to cyanazine is largely influenced by root uptake. During periods of active plant growth, conditions favorable for rapid root uptake of cyanazine were responsible for the greatest corn injury. Introduction Postemergence applications of cyanazine have pro- vided good control of annual grasses (2, 3). However, in some instances weed control has'been variable and corn injury has occurred. Herbicide rate, stage of plant growth, soil interception of spray, rainfall, and adjuvants have 74 75 been suggested as factors in determining the degree of cyanazine injury to corn (1, 2, 3, 5). Injury to corn seedlings treated with atrazine has been reported under cold, wet conditions (7). The research- ers concluded that low temperatures decreased the rate of detoxification from foliarly-absorbed atrazine in the stressed plants. They suggested that reduced detoxifica- tion by the roots did not contribute to the death of the corn. The interception of the postemergence spray by the soil and the subsequent herbicide uptake by plant roots may also play a role in determining plant responses to postemergence herbicide applications. Greater control of giant foxtail (Setaria faberii Herrm.) in the 4 to 5-leaf stage was achieved when atrazine was applied to wet soil followed by simulated rainfall than when rainfall did not occur (6). Although root absorption of cyanazine was found to supplement foliar uptake resulting in corn phytotoxicity, the extent of direct root uptake was not measured (4). Previous studies with cyanazine suggested that rapid root uptake could result in an overloaded detoxification mechanism. lKern, A. D., w. F. Meggitt, and D. Penner. 1974. Absorption, translocation, and metabolism of foliar applied cyanazine in corn, fall panicum, and green foxtail. Weed Sci. Soc. Amer. Abstr. No. 194. 76 Occurrence of cyanazine injury may result if sufficient soil residual were available at a time of rapid uptake of water and the herbicide. The Objective of this investigation was to determine the role that root uptake of cyanazine plays in corn injury due to postemergence applications. The effects of applica- tion rate and soil moisture on tolerance to soil-applied cyanazine prior to corn emergence or when the corn had four leaves was determined. Materials and Methods 'Michigan 396' corn seed was planted in 946-ml cups containing a Conover sandy loam soil with 2.4% organic mat— ter and grown in the greenhouse. The corn was thinned to three plants per cup and grown at 23 to 27 C with supplement— al lighting of 12.9 klux during a l6-hr day. Preemergence herbicide applications were made im- mediately after planting. Postemergence herbicide treat- ments were made directly to the soil with a pipette when the corn had four leaves. Applications of 20 m1 of the herbicide solution was made to dry soil. The mixture was applied slowly to insure against absorption by the base of the corn Shoot. The plants were supplied with a modified Hoagland's no. 1 solution every 3 days. Soil moisture levels were maintained under low and high regimes of 25 and 50 ml water per pot, respectively. If plants under the low 77 moisture conditions began to wilt, small amounts of water were added. Shoot dry weight was recorded when the plants had 5 to 6 leaves. One preemergence study was harvested at the 3, 4, and 5-leaf stages for dry weight comparison over time. Thus, corn treated with preemergence applications of the herbicides were grown in treated soil for 16 to 25 days. The corn was harvested 10 days after the postemerg- ence treatments. Data presented are the means of two ex- periments with three or four replications. Results and Discussion Both soil moisture level and herbicide rate had a pronounced effect on corn tolerance to preemergence appli— cations of cyanazine (Table 1). Reduction in dry weight was greatest under high soil moisture conditions. Although cyanazine rates of 1.1 to 4.5 kg/ha reduced corn growth, applications of 5.6 and 6.7 kg/ha resulted in about a 50% loss in dry weight of 25—day—old corn grown under high soil moisture conditions. Similar reductions in dry weight from cyanazine were Obtained under the low moisture regime. In comparison, excellent tolerance to atrazine was Observed. Rapid conversion of absorbed atrazine to hydroxy-atrazine was prObably responsible for good corn tolerance under these conditions. During preliminary experiments which gave similar results, reduced corn vigor was not visually observed until the plants reached the 3 to 4-leaf stage. 78 Table 1. Effect of preemergence applications of cyanazine and atrazine to corn grown in the greenhouse under two moisture regimes.a Dry weight Treatment rate Low moisture High moisture (ks/ha) (s/3 plants) (S/3 plantS) Cyanazine 0.0 1.60 a 2.32 a 1.1 1.44 abc 1.92 bc 2.2 1.33 bcd 1.71 cd 3.4 1.27 cde 1.76 cd 4.5 1.12 de 1.55 d 5.6 1.11 e 1.27 e 6.7 1.13 de 1.08 e Atrazine 2.2 1.55 ab 2.09 ab 4.5 1.51 ab 1.94 bc 6.7 1.54 ab 2.28 a aMeans within columns with Similar letters are not significantly different at the 5% level by Duncan's Multi- ple Range Test. 79 The data in Table 2 indicates that corn harvested in the 5-leaf stage showed the greatest rate response to preemergence applications of cyanazine. This effect may be explained by the increased time interval for cyanazine uptake and the more rapid cyanazine uptake by the larger plants. Experimental conditions permitted cyanazine leach- ing into the root zone. With the exception of the 4.5 kg/ha rate under low moisture, corn showed good tolerance to atrazine applied to the soil when the corn had four leaves (Table 3). How- ever, rates of 2.2 and 4.5 kg/ha of cyanazine significantly reduced the growth of corn 10 days following soil applica- tion. Corn at this stage appeared unable to detoxify the large amounts of cyanazine absorbed from the soil rapidly enough to prevent injury. Similar responses have been Observed in the field 10 to 20 days after cyanazine treat- ment.2 However, the corn appeared to compensate for the reduction in growth as the growing season continued. The coefficient of correlation and linear regres- sion (Figure 1 and 2) indicated that the decrease in corn shoot dry weight as influenced by an increase in cyanazine was not as great under the low moisture regime as under 2Kern, A. D., N. F. Meggitt, and R. 0. Bond. 1972. Green foxtail control in Michigan. N. Cent. Weed Contr. Conf. Res. Rep. 29:144. 80 Table 2. Reduction in dry weight of corn harvested at three different stages of growth following preemergence treatments of cyanazine.a Dry weight Cyanazine 3-1eaf 4-leaf 5-leaf (kg/ha) (% of control) 0 100.0 a 100.0 a 100.0 a 2 100.0 a 93.5 ab 92.6 b 4 97.7 85.9 b 67.1 c 6 78.2 b 81.2 be 60.4 C aMeans within columns with similar letters are not significantly different at the 5% level by Duncan's Multi- ple Range Test. 81 Table 3. Influence of atrazine and cyanazine on corn growth 10 days after soil treatment when the corn had four leaves.a Dry weight Treatment Rate Low moisture High moisture (kg/ha) (gm/3 plants) (gm/3 plants) Control 0.0 1.78 a 2.29 a Atrazine 2.2 1.57 ab 2.13 ab Atrazine 4.5 1.45 be 1.98 ab Cyanazine 2.2 1.33 cd 1.56 c Cyanazine 4.5 1.18 d 1.30 cd aMeans within columns with similar letters are not significantly different at the 5% level by Duncan's Multi- ple Range Test. 82 2.2- r = —.836** 2.04 L 1.8- Dry wt. Per 3 plants 0.84 1 I W T I T ' 1.1 2.2 3.4 4.5 5.6 657 Cyanazine (kg/ha) Figure 1. ielationship between the rate of cyanazine application and plant dry weight 10 days after treating corn with four leaves and maintained under low soil moisture conditions. 2.4» Dry wt. per 3 plants ' T 1.1 2:2 3:4 41.5 5.6 6.7 Cyanazine (kg/ha) Figure 2. Relationship between the rate of cyanazine application and plant dry weight 10 days after treating corn with four leaves and maintained under high soil moisture conditions. 84 high moisture conditions. Repeated experiments gave similar results with significant values. Figure 3 shows that corn injury from cyanazine applied to the soil resulted in small- er and less turgid plants. Although color was not always an Obvious injury indicator on marginally injured plants, corn treated with 5.6 and 6.7 kg/ha of cyanazine were dis- tinguishably more chlorotic. The same plants grown under high moisture conditions became flaccid. Results of this study indicate that corn tolerance to cyanazine is largely influenced by root uptake. Soil type, rainfall after treatment, and weed or crop situations favoring soil interception of the spray are contributors to cyanazine phytotoxicity to corn from postemergence treat- ments. The physiological stage of plant growth and other factors may be responsible for greater cyanazine uptake resulting in increased injury. 85 Figure 3. Response of corn to soil-applied postemergence treatments of cyanazine. The treated plants indiCate responses 10 days after treatment to soils maintained under low (A) and high (B) moisture regimes. 86 CYRNRZINE K G/ H H \ LOW MOIST. \ "‘ ‘ ‘ 1‘ Q: .‘g’ at? M w- ..H- H. LN 0.00 2.24 4.48 5.60 CYHNHZNE K GI H R HIGH MOIST. 7" ‘\ ” 419% f... i \ \ ——j 87 Literature Cited Hughes W. J., D. Jordan, and R. H. Schieferstein. l96é. SD 15418—-a new corn herbicide. Proc. Ninth Brit. Weed Cont. Conf. pp. 1018-1025. Kapusta, G. 1970. Corn growth stage tolerance to post—emergence applied SD-l5418. Proc. N. Cent. Weed Contr. Conf. 25:32-33. Kern, A. D. and W. F. Meggitt. 1972. Fall panicum control in corn with postemergence herbicide treat- ments. Proc. N. Cent. Weed Contr. Conf. 27:20. Kern, A. D., W. F. Meggitt, and D. Penner. 1974. Uptake, movement, and metabolism of cyanazine in fall panicum, green foxtail, and corn. Weed Sci. (In preparation). Nalewaja, J. D. 1972. Linseed oil and postemergence herbicides. Proc. Flax Institute of the U. S. 42:10-14. Thompson, L., Jr. and F. W. Slife. 1969. Foliar and root absorption of atrazine applied postemergence to giant foxtail. Weed Sci. 17:251-256. Thompson, L., Jr., F. W. Slife, and H. S. Butler. 1970. Environmental influence on the tolerance of corn to atrazine. Weed Sci. 18:509-514. CHAPTER 6 SUMMARY AND CONCLUSIONS In the field, postemergence treatments of cyanazine at 3.4 kg/ha applied to corn with less than five leaves and fall panicum with less than four leaves eliminated compet- ing fall panicum and provided sufficient soil residual for full-season control and maximum.yields. Control was re- duced Significantly when treatments were applied at later stages of growth. In addition, greater corn injury result- ed when cyanazine was applied to corn with six to seven leaves. Yield reductions as a result of late treatments were due to both crop injury and weed competition. Greenhouse and field studies showed that phytObland oils increased both fall panicum and corn injury by cyana- zine. These Observations were confirmed with radiotracer studies. It appeared that selectivity from postemergence cyanazine treatment was partially due to the slow entry of the herbicide into the corn leaves. With oil large amounts of the herbicide were concentrated in the leaves of corn 5 days after foliar treatment. This may be the reason for foliar injury Observed in the field following postemergence applications of cyanazine plus oil. Because of the narrowed 88 89 margin of selectivity and erratic results, the addition of adjuvants to cyanazine are not recommended. Corn absorbed less cyanazine from foliar applica- tions and more from root treatments when compared to the weed species. Absorbed cyanazine was rapidly translocated acropetally from point of application to areas of highest transpiration in'both weeds and corn. Slower inactivation of cyanazine by fall panicum and green foxtail plays a role in selectivity following root treatment. Both the Shoots and roots of green foxtail contained larger amounts of unaltered cyanazine following foliar and root applications of the herbicide. Greater sensitivity of green foxtail than fall panicum to cyanazine is related to its inability to alter the parent compound. Following foliar and root treatments of cyanazine, corn appeared to metabolize the herbicide to two stable hydroxy compounds. Greater amounts of the breakdown pro- ducts were found 5 days after the foliar treatment than after one day of treatment in all three species. In con- trast to corn, fewer metabolites were found in the weedy grasses. Sufficient amounts of root-applied cyanazine reached a sensitive Site in fall panicum for effective kill. Although treatments restricted to the foliage re- duced fresh weight, complete fall panicum and green foxtail control was the result of both foliar and root absorption. 90 Similarly, greater corn injury was Observed when soil interception of the herbicide was allowed. Therefore, corn tolerance is influenced by root uptake of the postemergence spray. Field conditions favoring cyanazine movement into the root zone of vigorously growing corn results in rapid uptake of the herbicide overloading the detoxification mechanism resulting in injury. In conclusion, selectivity is not solely based on foliar uptake, but also on the proportion taken up by foliage and roots. Many factors influence the contribution of each pathway of uptake to selectivity. Under conditions favorable for root uptake, the margin of selectivity may 'be reduced. CrOp pOpulation, weed density, soil type, and rainfall are factors contributing to the effectiveness of cyanazine for annual grass control and on phytotoxicity to the crOp. These factors influence the amount of soil inter- ception from postemergence application of cyanazine. LIST OF REFERENCES 10. LIST OF REFERENCES AkObundu, I. 0., R. D. Sweet, W. B. Duke, and P. L. Minotti. 1972. Synergistic effect of atrazine and alachlor combinations of Japanese millet. Weed Sci. Soc. Amer. Abstr. No. 185. Alex, J. F. 1972. Panic(um) in Ontario. Agrichemical Age 15(3):l6. Anonymfiusé 1972. Fall panicum. Agrichemical Age 15 : . Ashton, F. M. and A. S. Crafts. 1973. Mode of Action of Herbicides. Wiley-Interscience, New York, New York. 504 pp. Bauman, T. T. and J. L. Williams, Jr. 1973. Tillage influence on corn herbicide performance in fall pgnicum trials. Proc. N. Cent. Weed Contr. Conf. 2 :77. Bayer, D. E. and K. P. Buckholtz. 1957. The influence of preemergence treatments with simazine and several isomers on yield of corn and of weeds. N. Cent. Weed Contr. Conf. Res. Rep. 14:86-87. Bell, D. T. and D. E. Koeppe. 1972. Noncompetitive effects of giant foxtail on growth of corn. Agron. J. 64:321-325. Beynon, K. I. 1972. The analysis of crops and soils for the triazine herbicide cyanazine and some of its degradation products. I. Development of method. Pestic. Sci. 3:389-400. Beynon, K. I., P. Bosio, and K. E. Elgar. 1972. The analysis of crops and soils for the triazine herbi- cide cyanazine and some of its degradation products. II. Results. Pestic. Sci. 3:401-408. Beynon, K. I., G. Stoydin, and A. N. Wright. 1972. The breakdown of the triazine herbicide cyanazine in soils and maize. Pestic. Sci. 3:293-305. 91 ll. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 92 Beynon, K. I., G. Stoydin, and A. N. Wright. 1972. The breakdown of the triazine herbicide cyanazine in wheat and potatoes grown under indoor conditions in treated soils. Pestic. Sci. 3 379-387. Beynon, K. I., G. Stoydin, and A. N. Wright. 1972. A comparison of the breakdown of the triazine herbicides cyanazine, atrazine, and simazine in soils and in maize. Pestic. Biochem. and Physiol. 2:153-161. Bunting, E. S. and J. W. Ludwig. 1964. Plant compe- tition and weed control in maize. Seventh British Weed Contr. Conf. Proc. 1:385—388. Burnside, O. C. and G. A. Wicks. 1967. The effect of weed removal treatments on sorghum growth. Weeds 15:204—207. Burr, R. J. and G. F. Warren. 1971. Enhancement of herbicide activity with an isoparaffinic oil carrier. Weed Sci. 19:701-705. Crayford, J. V. and D. H. Hutson. 1972. The metabo— lism of the herbicide, 2-chloro-4-(ethylamino)-6- (l-cyano-l-methylamino)-s-triazine in the rat. Pestic. Biochem. and PhySiol. 2:295-307. Dexter, A. C., O. C. Burnside, and T. L. Lavy. 1966. Factors influencing the phytotoxicity of foliar applications of atrazine. Weeds luz222—228. Duke, W. B. 1968. Atrazine versus atrazine plus oil. Proc. Northeast. Weed Contr. Conf. 23:286-292. Frank, R. and G. J. Sirons. 1973. Soil residues and plant uptake of atrazine and cyanazine. Weed Sci. Soc. Amer. Abstr. No. 176. Gleason, H. A. and A. Cronquist. 1963. Mannual of Vascular Plants. Van Nostrand Reinhold Co. New York. pp. 105-106. Hartwig, N. L. 1972. Fall panicum. Agrichemical Age 15( )z5. Hartwig, N. L. and F. S. Serdy. 1971. Control of fall panicum in field corn. Proc. Northeast. Weed Contr. Conf. 25:323—327. Houghton, J. M. 1970. Panicum control. Illinois Custom Operators Spray School 22:49-50. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 93 Houghton, J. M. and F. W. Slife. 1969. Environmental factors that effect the development and control of Panicum species. Proc. N. Cent. Weed Contr. Conf. Hoveland, C. S. and G. A. Buchanan. 1972. Flooding tolerance of fall panicum and Texas panicum. Weed Hughes W. J., D. Jordan, and R. H. Schieferstein. 1968. SD 15418--a new corn herbicide. Proc. Ninth Brit. Weed Contr. Conf. pp. 1018-1025. Hutson, D., E. C. Hoadley, M. H. Griffiths, and C. Donninger. 1970. Mercaptic acid formation in the metabolism of 2-chloro-4-ethylamino-6-(l-methyl-l- cyanoethylamino)-§7triazine in the rat. J. Agr. Food Chem. 18:507-512. Jones, G. E. and G. W. Anderson. 1964. Atrazine as a foliar application in oil water emulsion. Proc. N. Cent. Weed Contr. Conf. 11:27-29. Kapusta, G. 1970. Corn growth stage tolerance to post—emergence applied SD-15418. Proc. N. Cent. Weed Contr. Conf. 25:32-33. Kapusta, G. 1970. Delayed planting influence on soybean tolerance to SD-l5418 treated soil. Proc. N. Cent. Weed Contr. Conf. 25:44—45. Kearney, P. C. and D. D. Kaufman. 1969. Degradation of Herbicides. Marcel Dekker, Inc., New York. 394 pp. Kern, A. D. and W. F. Meggitt. 1972. Fall panicum control in corn with postemergence herbicide treatments. Proc. N. Cent. Weed Contr. Conf. 27:20. Kern, A. D., W. F. Meggitt, and R. C. Bond. 1972. Green foxtail control in Michigan. N. Cent. Weed Contr. Conf. Res. Rep. 29:144. Kern, A. D., W. F. Meggitt, and R. C. Bond. 1973. Green foxtail and common lambsquarter control in Northern Michi an. N. Cent. Weed Contr. Conf. Res. Rep. 30:1 6. Kern, A. D., W. F. Meggitt, and D. Penner. 1974. Absorption, translocation, and metabolism of foliar applied cyanazine in corn, fall panicum, and green foxtail. Weed Sci. Soc. Amer. Abstr. No. 194. 36. 37- 38. 39. 40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 94 Knake, E. L. 1968. Atrazine as a postemergence spray. Illinois Custom Operators Spray School 20:93-97. Knake, E. L. and F. W. Slife. 1969. Effect of time of giant foxtail removal from corn and soybeans. Weeds Sci. 17: 281—283. Knake, E. L. and F. W. Slife. 1965. Giant foxtail seeded at various times in corn and soybeans. Weeds 13:331—334. McGlamery, M. D. 1971. The use of oils in post- emergence weed sprays. Weeds Today 2(1):13. Miller, S. D. and J. D. Nalewaja. 1973. Effect of additives upon phenmedipham for weed control in sugarbeets. Weed Sci. 21:67-70. Nalewaja, J. D. 1968. Postemergence atrazine treatments for weed control in corn. Proc. N. Cent. Weed Contr. Conf. 23:12-13. Nalewaja, J. D. 1972. Linseed oil and postemergence herbicides. Proc. Flax Institute of the U. S. Nalewaja, J. D., J. Pudelko, and B. Skopiec. 1973. Influence of oil additives on foxtail control with cyanazine. Proc. N. Cent. Weed Contr. Conf. 28:79. Oliver, D. W. and J. D. Bandeen. 1972. Persistence of atrazine, SD—l54l8, and S-6115 under corn. Weed Sci. Soc. Amer. Abstr. No. 194. Oliver, L. R. and M. M. Schreiber. 1971. Differential selectivity of herbicides on six Setaria taxa. Weed Sci. 19:428-431. ‘7'"“" Parochetti, J. V. 1970. The ten worst weeds of field crops: Panicums. Crops and Soils 22(9):12-l4. Parochetti, J. V. 1974. Yellow nutsedge, giant green foxgai%, and fall panicum control in corn. Weed Sci. 22: 0— 2. Pruss, S. W. 1969. Control of fall panicum (Panicum dichotomiflorum) in corn with triazine herbicides. I&oc. Nbrtheast. Weed Contr. Conf. 23:182-188. Radosevich, S. R. and A. P. Appleby. 1973. Relative susceptibility of two common groundsel (Senecio vulgaris L.) biotype to six sftriazines. Agron. J. 50. 51. 52. 53- 54. 55- 56. 57. 58. 59. 60. 61. 62. 95 Roeth, F. W. and T. L. Lavy. 1971. Atrazine uptake by sudangrass, sorghum, and corn. Weed Sci. 19193-97. Ryan, G. F. 1970. Resistance of common groundsel to simazine and atrazine. Weed Sci. 18:614-616. Schnappinger, M. G., Jr. and H. P. Wilson. 1972. Fall panicum control in Virginia. Agrichemical Age 15(3):16. Schnappinger, M. G., Jr. and H. P. Wilson. 1972. Ratios of atrazine and simazine for the control of fall panicum in corn. Proc. Northeast. Weed Sci. Soc. 27:4-9. Schneider, E. 0. 1957. Progress on simazine and the related compounds. Proc. N. Cent. Weed Contr. Conf. 14:43-44. Schrader, J. W. 1970. The Influence of Oil and Envi- ronmental Factors on Phytotoxicity and Foliar Pene- tration of Atrazine. Ph. D. Thesis. Michigan State University. 98 pp. Serdy, F. S. The Effect of Competition, Herbicides, and Ethylene on Germination, Growth, and DevelOp— ment of Fall Panicum. Ph. D. Thesis. The Penn- sylvania State University. 78 pp. Shimabukuro, R. H. 1967. Atrazine metabolism and herbicidal selectivity. Plant Physiol. 42:1269-1276. Shimabukuro, R. H. 1967. Significance of atrazine dealkylation in root and shoot of pea plants. J. Agr. Food Chem. 15 557-562. Shimabukuro, R. H., R. E. Kadunce, and D. S. Frear. 1966. Dealkylation of atrazine in mature pea plants. J. Agr. Food Chem. 14:392-395. Shimabukuro, R. H. and H. R. Swanson. 1969. Atrazine metabolism, selectivity, and mode of action. J. Agr. Food Chem. 17:199-205. Shimabukuro, R. H., H. R. Swanson, and W. C. Walsh. 1970. Glutathione conjugation. Plant Physiol. Smith, C. N., Jr. and J. D. Nalewaja. 1972. Uptake and translocation of foliarly-applied atrazine. Weed Sci. 20:36-40. 63. 64. 65. 66. 67. 68. 69. 70. 71. 72. 73. 74. 75- 96 Smith, W. F. and R. D. Ilnicki. 1972. Effects of atrazine and Ca and P on fall panicum plants col— lected from selected sites in New Jersey. Weed Sci. Soc. Amer. Abstr. No. 48. Smith, W. F. and R. D. Ilnicki. 1972. The effects of atrazine and simazine on physiological processes of fall panicum. Proc. Northeast. Weed Contr. Conf. 26:79. Staniforth, D. W. 1957. Effects of annual grass weeds on the yield of corn. Agron. J. 49:551-555. Strand, 0. E. 1970. A comparison of linseed oil and other adjuvants used with atrazine for early post- emergence weed control in corn. Proc. Flax Insti- tute of the U. S. 40:23-24. Strand, 0. E. and R. Behrens. 1970. Effect of adju- vants on weed control in corn with atrazine, 1970. N. Cent. Res. Rep, 27:77, Sylwester, E. P. 1970. Foxtails. Crops and Soils 22(4):11-13. Taft, L. G., E. W. Stroube, and L. E. Bendixen. 1973. Residue analysis of five triazine herbicides in soil by gas chromatography. Weed Sci. Soc. Abstr. No. 175. Thompson, L., Jr. 1972. Metabolism of chloro s- triazine herbicides by Panicum and Setaria. Weed Sci. 20:584-587. Thompson, L., Jr., J. M. Houghton, F. W. Slife, and H. S. Butler. 1971. Metabolism of atrazine by fall panicum and large crabgrass. Weed Sci. 19:409-412. Thompson, L., Jr., R. W. Schumacher, and C. E. Rieck. 1974. An atrazine resistant strain of redroot pig— weed. Weed Sci. Soc. Abstr. No. 196. Thompson, L., Jr. and F. W. Slife. 1969. Foliar and root absorption of atrazine applied postemergence to giant foxtail. Weed Sci. 17:251-256. Thompson, L., Jr. and F. W. Slife. 1970. Root and foliar absorption of atrazine ap lied postemergence to broadleaf weeds. Weed Sci. 1 :349-351. Thompson, L., Jr., F. W. Slife, and H. 8. Butler. 1970. Environmental influence on the tolerance of corn to atrazine. Weed Sci. 18:509-514. 76. 77- 78. 79. 80. 81. 82. 83. 84. 85. 97 Thompson, R. P. an? F. W. Slife. 1973. Uptake and degradation of 4C-Bladex and l C-atrazine by four crop and two weed species. Weed Sci. Soc. Amer. Abstr. No. 142. Thompson, R. P. and F. W. Slife. 1973. Use of soy- beans as a rescue crop following cyanazine applica- tions to corn. Proc. N. Cent. Weed Contr. Conf. 28:53. U. S. Department of Agriculture. Agricultural Research Service. 1968. Extent and Cost of Weed Control with Herbicides and an Evaluation of Important Weeds, 1965. ABS 34-102. 85 pp. U. S. Department of Agriculture. Agricultural Research Service. 1970. Selected Weeds of the United States. Agr. Handbook No. 366. 463 pp. Vengris, J. 1973. Fall panicum control in field corn in Massachusetts, 1972. Proc. Northeast. Weed Contr. Conf. 27:52-55. Vengris, J. 1972. Fall panicum.control in field corn wgth triazines. Proc. Northeast. Weed Contr. Conf. 2 :1-30 Weed Science Society of America. 1970. Herbicide Handbook. 2nd ed. W. F. Humphrey Press, Inc., Geneva, New York. 368 pp. Wicks, G. A., C. R. Fenster, 0. C. Burnside, and R. S. Moomaw. 1970. Weed control in corn with herbicides across Nebraska in 1970. Proc. N. Cent. Weed Contr. Conf. 25:36—43. Woogerd, S. M. 1971. Agricultural Spray Adjuvants. Washington Pest Control Handbook. Washington State University. Washin ton State Department of Agri— culture. pp. 177-1 1. Wright, W. G. 1966. Use of atrazine in water plus oil for weed control in corn. Proc. N. Cent. Weed Contr. Conf. 21:44-45. APPENDICES 98 APPENDIX A Modified Hoagland's No. 1 Solution KH2P04 KNO3 Ca(N0 2°4H20 3) MgSOu~7H20 g/L MnCL °4H20 3 g/L H3B04 g/L ZnCl 0 N) +4 e: F4 +4 H 41 U1 \fi :3 2: 3 Z 2 0.05 g/L CuCl -2H 0 2 2 0.05 g/L Moo3 26.3 g/L SequestreneR pH 6.5 to 6.8 with 1 M NaOH [\DUOIUI'D ml/L ml/L ml/L ml/L ml/L ml/L 99 APPENDIX B Table B. Effect of spray volume and simulated rainfall on the efficacy of cyanazine at 2.2 kg/ha with and without oil on 9 to 10-cm fall panicum.a T — Fresh weightb Application spray volume Treatment Rate 234 L/ha 935 L/ha 935+L/haC (ks/ha) (s/cup) (s/cup) (s/cup) Control -- 6.7 ab 7.0 a 6.7 ab Cyanazine 2.2 5.4 be 3.2 cde 3.8 cd Cyanazine+oil 2.2+9.4 L/ha 3.6 cd 2.6 de 1.1 e aPlants were blocked as to density. Means followed by similar letters are not Signifi- cantly different at the 5% level by Duncan's Multiple Range Test. CSimulated rainfall equal to 2.5 cm was added immediately after treatment. 100 APPENDIX C Table 0. Influence of rainfall and relative humidity on the control of 10-cm fall panicum.25 days follow— ing treatment with cyanazine at 2.8 kg/ha with and without oil. Visual control ratinga Condition Cyanazine Cyanazine + 011 (%) (%> Control 0.0 0.0 Treated control 4.8 6.0 Rainb 4.3 7.3 (Rain)2 5.3 8.0 (Rain)2-no soil contactC 3.0 8.0 High humidityd 2.3 6.5 a0 = no control; 10 = complete control or kill. bSimulated rainfall equal to 2.5 cm was added immediately after foliage treatment had dried. CWashing of herbicide was prevented by tilting cup to Side. dHigh relative humidity of 75 to 80 was maintained with a vaporizer. A relative humidity of 40 to 45 was maintained for the other treatments. 101 APPENDIX D 100 90 80 7O 60 Percent reduction in stand 50 40 2O : lO 4 o L :. ' r I “r fi 20 4O 6O 80 100 120 140 160 Plant density (Shoots/cup) Figure 1. The relationship between plant density and the percent reduction in stand of fall panicum 14 days following cyanazine treatment of 3.4 kg/ha to 8-cm tall plants. “Miiiiiiiiiimniilt